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 $72.32   4.456%   $75.5426   $75.54   $75.55   $75.50  
  Purchase #2 $225.45   12.421%   $253.4531   $253.45   $253.45   $253.50  
  Purchase #3 $120.81   13.639%   $137.2873   $137.29   $137.30   $137.30  
  Purchase #4 $93.98   3.558%   $97.3238   $97.32   $97.30   $97.30  
  Purchase #5 $156.65   4.205%   $163.2371   $163.24   $163.25   $163.20  
  Purchase #6 $171.28   4.360%   $178.7478   $178.75   $178.75   $178.70  
  Purchase #7 $228.39   7.734%   $246.0537   $246.05   $246.05   $246.10  
  7 purchase totals = $1,068.88       $1,151.6454   $1,151.64   $1,151.65   $1,151.60