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 $215.32   8.791%   $234.2488   $234.25   $234.25   $234.20  
  Purchase #2 $220.57   12.109%   $247.2788   $247.28   $247.30   $247.30  
  Purchase #3 $204.54   13.406%   $231.9606   $231.96   $231.95   $232.00  
  Purchase #4 $237.51   5.860%   $251.4281   $251.43   $251.45   $251.40  
  Purchase #5 $148.29   8.792%   $161.3277   $161.33   $161.35   $161.30  
  Purchase #6 $86.58   8.334%   $93.7956   $93.80   $93.80   $93.80  
  Purchase #7 $220.32   3.727%   $228.5313   $228.53   $228.55   $228.50  
  7 purchase totals = $1,333.13       $1,448.5709   $1,448.58   $1,448.65   $1,448.50