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 $193.98   4.290%   $202.3017   $202.30   $202.30   $202.30  
  Purchase #2 $59.92   11.750%   $66.9606   $66.96   $66.95   $67.00  
  Purchase #3 $244.26   5.685%   $258.1462   $258.15   $258.15   $258.10  
  Purchase #4 $56.74   7.102%   $60.7697   $60.77   $60.75   $60.80  
  Purchase #5 $120.90   7.485%   $129.9494   $129.95   $129.95   $129.90  
  Purchase #6 $230.94   13.541%   $262.2116   $262.21   $262.20   $262.20  
  Purchase #7 $34.32   6.555%   $36.5697   $36.57   $36.55   $36.60  
  7 purchase totals = $941.06       $1,016.9089   $1,016.91   $1,016.85   $1,016.90