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 $62.52   3.574%   $64.7545   $64.75   $64.75   $64.80  
  Purchase #2 $141.38   7.525%   $152.0188   $152.02   $152.00   $152.00  
  Purchase #3 $194.86   8.410%   $211.2477   $211.25   $211.25   $211.20  
  Purchase #4 $204.92   6.789%   $218.832   $218.83   $218.85   $218.80  
  Purchase #5 $216.48   4.563%   $226.358   $226.36   $226.35   $226.40  
  Purchase #6 $56.89   9.587%   $62.344   $62.34   $62.35   $62.30  
  Purchase #7 $200.30   5.539%   $211.3946   $211.39   $211.40   $211.40  
  7 purchase totals = $1,077.35       $1,146.9496   $1,146.94   $1,146.95   $1,146.90