Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $145.34   11.438%   $161.964   $161.96   $161.95   $162.00  
  Purchase #2 $214.31   10.762%   $237.374   $237.37   $237.35   $237.40  
  Purchase #3 $138.95   5.303%   $146.3185   $146.32   $146.30   $146.30  
  Purchase #4 $193.33   9.477%   $211.6519   $211.65   $211.65   $211.70  
  Purchase #5 $137.78   10.229%   $151.8735   $151.87   $151.85   $151.90  
  Purchase #6 $119.94   8.559%   $130.2057   $130.21   $130.20   $130.20  
  Purchase #7 $112.71   6.653%   $120.2086   $120.21   $120.20   $120.20  
  7 purchase totals = $1,062.36       $1,159.5962   $1,159.59   $1,159.50   $1,159.70