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 $59.86   3.609%   $62.0203   $62.02   $62.00   $62.00  
  Purchase #2 $183.36   9.431%   $200.6527   $200.65   $200.65   $200.70  
  Purchase #3 $235.52   3.716%   $244.2719   $244.27   $244.25   $244.30  
  Purchase #4 $216.67   5.443%   $228.4633   $228.46   $228.45   $228.50  
  Purchase #5 $243.80   4.572%   $254.9465   $254.95   $254.95   $254.90  
  Purchase #6 $81.56   7.774%   $87.9005   $87.90   $87.90   $87.90  
  Purchase #7 $12.34   8.461%   $13.3841   $13.38   $13.40   $13.40  
  7 purchase totals = $1,033.11       $1,091.6393   $1,091.63   $1,091.60   $1,091.70