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 $140.84   9.400%   $154.079   $154.08   $154.10   $154.10  
  Purchase #2 $100.39   13.219%   $113.6606   $113.66   $113.65   $113.70  
  Purchase #3 $17.64   7.871%   $19.0284   $19.03   $19.05   $19.00  
  Purchase #4 $168.93   3.198%   $174.3324   $174.33   $174.35   $174.30  
  Purchase #5 $204.60   4.521%   $213.85   $213.85   $213.85   $213.90  
  Purchase #6 $119.49   9.822%   $131.2263   $131.23   $131.25   $131.20  
  Purchase #7 $246.66   6.231%   $262.0294   $262.03   $262.05   $262.00  
  7 purchase totals = $998.55       $1,068.2061   $1,068.21   $1,068.30   $1,068.20