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 $56.54   10.106%   $62.2539   $62.25   $62.25   $62.30  
  Purchase #2 $54.48   5.267%   $57.3495   $57.35   $57.35   $57.30  
  Purchase #3 $236.28   4.662%   $247.2954   $247.30   $247.30   $247.30  
  Purchase #4 $241.52   10.871%   $267.7756   $267.78   $267.80   $267.80  
  Purchase #5 $211.27   8.825%   $229.9146   $229.91   $229.90   $229.90  
  Purchase #6 $5.58   10.835%   $6.1846   $6.18   $6.20   $6.20  
  Purchase #7 $201.49   13.147%   $227.9799   $227.98   $228.00   $228.00  
  7 purchase totals = $1,007.16       $1,098.7535   $1,098.75   $1,098.80   $1,098.80