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 $95.59   6.389%   $101.6972   $101.70   $101.70   $101.70  
  Purchase #2 $30.45   11.642%   $33.995   $34.00   $34.00   $34.00  
  Purchase #3 $65.38   11.324%   $72.7836   $72.78   $72.80   $72.80  
  Purchase #4 $240.33   8.450%   $260.6379   $260.64   $260.65   $260.60  
  Purchase #5 $144.53   6.158%   $153.4302   $153.43   $153.45   $153.40  
  Purchase #6 $209.83   12.363%   $235.7713   $235.77   $235.75   $235.80  
  Purchase #7 $228.41   9.348%   $249.7618   $249.76   $249.75   $249.80  
  7 purchase totals = $1,014.52       $1,108.0770   $1,108.08   $1,108.10   $1,108.10