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 $68.44   5.479%   $72.1898   $72.19   $72.20   $72.20  
  Purchase #2 $247.96   8.379%   $268.7366   $268.74   $268.75   $268.70  
  Purchase #3 $235.60   7.651%   $253.6258   $253.63   $253.65   $253.60  
  Purchase #4 $39.98   7.375%   $42.9285   $42.93   $42.95   $42.90  
  Purchase #5 $233.44   5.411%   $246.0714   $246.07   $246.05   $246.10  
  Purchase #6 $175.34   8.352%   $189.9844   $189.98   $190.00   $190.00  
  Purchase #7 $80.52   6.607%   $85.84   $85.84   $85.85   $85.80  
  7 purchase totals = $1,081.28       $1,159.3765   $1,159.38   $1,159.45   $1,159.30