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 $58.54   4.865%   $61.388   $61.39   $61.40   $61.40  
  Purchase #2 $150.38   13.367%   $170.4813   $170.48   $170.50   $170.50  
  Purchase #3 $116.78   10.689%   $129.2626   $129.26   $129.25   $129.30  
  Purchase #4 $227.35   10.782%   $251.8629   $251.86   $251.85   $251.90  
  Purchase #5 $232.35   10.337%   $256.368   $256.37   $256.35   $256.40  
  Purchase #6 $138.42   11.491%   $154.3258   $154.33   $154.35   $154.30  
  Purchase #7 $197.70   7.229%   $211.9917   $211.99   $212.00   $212.00  
  7 purchase totals = $1,121.52       $1,235.6803   $1,235.68   $1,235.70   $1,235.80