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 $94.43   10.777%   $104.6067   $104.61   $104.60   $104.60  
  Purchase #2 $77.94   8.862%   $84.847   $84.85   $84.85   $84.80  
  Purchase #3 $208.79   12.683%   $235.2708   $235.27   $235.25   $235.30  
  Purchase #4 $113.32   11.404%   $126.243   $126.24   $126.25   $126.20  
  Purchase #5 $161.80   10.274%   $178.4233   $178.42   $178.40   $178.40  
  Purchase #6 $194.98   8.736%   $212.0135   $212.01   $212.00   $212.00  
  Purchase #7 $167.29   9.279%   $182.8128   $182.81   $182.80   $182.80  
  7 purchase totals = $1,018.55       $1,124.2171   $1,124.21   $1,124.15   $1,124.10