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 $38.95   10.742%   $43.134   $43.13   $43.15   $43.10  
  Purchase #2 $154.33   13.404%   $175.0164   $175.02   $175.00   $175.00  
  Purchase #3 $167.61   5.683%   $177.1353   $177.14   $177.15   $177.10  
  Purchase #4 $62.76   9.537%   $68.7454   $68.75   $68.75   $68.70  
  Purchase #5 $218.68   3.625%   $226.6072   $226.61   $226.60   $226.60  
  Purchase #6 $140.79   7.455%   $151.2859   $151.29   $151.30   $151.30  
  Purchase #7 $198.91   5.868%   $210.582   $210.58   $210.60   $210.60  
  7 purchase totals = $982.03       $1,052.5062   $1,052.52   $1,052.55   $1,052.40