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 $56.55   4.298%   $58.9805   $58.98   $59.00   $59.00  
  Purchase #2 $235.25   10.734%   $260.5017   $260.50   $260.50   $260.50  
  Purchase #3 $171.88   6.700%   $183.396   $183.40   $183.40   $183.40  
  Purchase #4 $146.60   11.821%   $163.9296   $163.93   $163.95   $163.90  
  Purchase #5 $118.94   11.131%   $132.1792   $132.18   $132.20   $132.20  
  Purchase #6 $249.56   4.492%   $260.7702   $260.77   $260.75   $260.80  
  Purchase #7 $33.59   7.264%   $36.03   $36.03   $36.05   $36.00  
  7 purchase totals = $1,012.37       $1,095.7872   $1,095.79   $1,095.85   $1,095.80