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 $169.55   7.596%   $182.429   $182.43   $182.45   $182.40  
  Purchase #2 $42.85   7.547%   $46.0839   $46.08   $46.10   $46.10  
  Purchase #3 $140.77   7.246%   $150.9702   $150.97   $150.95   $151.00  
  Purchase #4 $211.31   4.461%   $220.7365   $220.74   $220.75   $220.70  
  Purchase #5 $59.70   7.758%   $64.3315   $64.33   $64.35   $64.30  
  Purchase #6 $121.68   9.362%   $133.0717   $133.07   $133.05   $133.10  
  Purchase #7 $229.66   11.575%   $256.2431   $256.24   $256.25   $256.20  
  7 purchase totals = $975.52       $1,053.8659   $1,053.86   $1,053.90   $1,053.80