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 $216.47   4.464%   $226.1332   $226.13   $226.15   $226.10  
  Purchase #2 $69.98   6.229%   $74.3391   $74.34   $74.35   $74.30  
  Purchase #3 $138.54   10.384%   $152.926   $152.93   $152.95   $152.90  
  Purchase #4 $119.48   10.780%   $132.3599   $132.36   $132.35   $132.40  
  Purchase #5 $56.32   8.634%   $61.1827   $61.18   $61.20   $61.20  
  Purchase #6 $169.96   5.788%   $179.7973   $179.80   $179.80   $179.80  
  Purchase #7 $55.58   6.435%   $59.1566   $59.16   $59.15   $59.20  
  7 purchase totals = $826.33       $885.8948   $885.90   $885.95   $885.90