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 $211.37   10.168%   $232.8621   $232.86   $232.85   $232.90  
  Purchase #2 $98.96   7.367%   $106.2504   $106.25   $106.25   $106.30  
  Purchase #3 $85.64   3.868%   $88.9526   $88.95   $88.95   $89.00  
  Purchase #4 $213.66   5.729%   $225.9006   $225.90   $225.90   $225.90  
  Purchase #5 $219.36   8.406%   $237.7994   $237.80   $237.80   $237.80  
  Purchase #6 $87.66   4.484%   $91.5907   $91.59   $91.60   $91.60  
  Purchase #7 $29.49   4.164%   $30.718   $30.72   $30.70   $30.70  
  7 purchase totals = $946.14       $1,014.0738   $1,014.07   $1,014.05   $1,014.20