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 $65.52   6.764%   $69.9518   $69.95   $69.95   $70.00  
  Purchase #2 $238.34   7.556%   $256.349   $256.35   $256.35   $256.30  
  Purchase #3 $11.36   3.590%   $11.7678   $11.77   $11.75   $11.80  
  Purchase #4 $247.92   11.429%   $276.2548   $276.25   $276.25   $276.30  
  Purchase #5 $183.32   6.332%   $194.9278   $194.93   $194.95   $194.90  
  Purchase #6 $193.38   5.378%   $203.78   $203.78   $203.80   $203.80  
  Purchase #7 $114.96   4.632%   $120.2849   $120.28   $120.30   $120.30  
  7 purchase totals = $1,054.80       $1,133.3161   $1,133.31   $1,133.35   $1,133.40