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 $64.30   11.611%   $71.7659   $71.77   $71.75   $71.80  
  Purchase #2 $43.37   5.121%   $45.591   $45.59   $45.60   $45.60  
  Purchase #3 $119.38   11.612%   $133.2424   $133.24   $133.25   $133.20  
  Purchase #4 $206.65   9.193%   $225.6473   $225.65   $225.65   $225.60  
  Purchase #5 $225.71   4.499%   $235.8647   $235.86   $235.85   $235.90  
  Purchase #6 $190.60   8.589%   $206.9706   $206.97   $206.95   $207.00  
  Purchase #7 $104.58   10.263%   $115.313   $115.31   $115.30   $115.30  
  7 purchase totals = $954.59       $1,034.3949   $1,034.39   $1,034.35   $1,034.40