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 $58.69   6.369%   $62.428   $62.43   $62.45   $62.40  
  Purchase #2 $91.74   8.231%   $99.2911   $99.29   $99.30   $99.30  
  Purchase #3 $243.97   10.439%   $269.438   $269.44   $269.45   $269.40  
  Purchase #4 $146.75   11.182%   $163.1596   $163.16   $163.15   $163.20  
  Purchase #5 $101.30   12.386%   $113.847   $113.85   $113.85   $113.80  
  Purchase #6 $162.85   10.369%   $179.7359   $179.74   $179.75   $179.70  
  Purchase #7 $190.85   6.282%   $202.8392   $202.84   $202.85   $202.80  
  7 purchase totals = $996.15       $1,090.7388   $1,090.75   $1,090.80   $1,090.60