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 $52.95   10.771%   $58.6532   $58.65   $58.65   $58.70  
  Purchase #2 $250.96   4.272%   $261.681   $261.68   $261.70   $261.70  
  Purchase #3 $85.94   9.434%   $94.0476   $94.05   $94.05   $94.00  
  Purchase #4 $74.27   6.109%   $78.8072   $78.81   $78.80   $78.80  
  Purchase #5 $37.96   4.435%   $39.6435   $39.64   $39.65   $39.60  
  Purchase #6 $205.26   6.427%   $218.4521   $218.45   $218.45   $218.50  
  Purchase #7 $128.36   6.532%   $136.7445   $136.74   $136.75   $136.70  
  7 purchase totals = $835.70       $888.0291   $888.02   $888.05   $888.00