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 $61.98   4.825%   $64.9705   $64.97   $64.95   $65.00  
  Purchase #2 $135.77   12.525%   $152.7752   $152.78   $152.80   $152.80  
  Purchase #3 $64.46   13.598%   $73.2253   $73.23   $73.25   $73.20  
  Purchase #4 $86.64   7.642%   $93.261   $93.26   $93.25   $93.30  
  Purchase #5 $206.85   12.640%   $232.9958   $233.00   $233.00   $233.00  
  Purchase #6 $98.40   4.253%   $102.585   $102.59   $102.60   $102.60  
  Purchase #7 $39.74   9.173%   $43.3854   $43.39   $43.40   $43.40  
  7 purchase totals = $693.84       $763.1982   $763.22   $763.25   $763.30