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 $85.73   10.467%   $94.7034   $94.70   $94.70   $94.70  
  Purchase #2 $188.74   7.254%   $202.4312   $202.43   $202.45   $202.40  
  Purchase #3 $94.93   4.453%   $99.1572   $99.16   $99.15   $99.20  
  Purchase #4 $224.28   3.747%   $232.6838   $232.68   $232.70   $232.70  
  Purchase #5 $65.55   4.502%   $68.5011   $68.50   $68.50   $68.50  
  Purchase #6 $121.39   4.122%   $126.3937   $126.39   $126.40   $126.40  
  Purchase #7 $212.83   11.462%   $237.2246   $237.22   $237.20   $237.20  
  7 purchase totals = $993.45       $1,061.0950   $1,061.08   $1,061.10   $1,061.10