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 $218.49   8.480%   $237.018   $237.02   $237.00   $237.00  
  Purchase #2 $220.72   10.692%   $244.3194   $244.32   $244.30   $244.30  
  Purchase #3 $16.66   4.634%   $17.432   $17.43   $17.45   $17.40  
  Purchase #4 $199.65   5.860%   $211.3495   $211.35   $211.35   $211.30  
  Purchase #5 $197.96   3.351%   $204.5936   $204.59   $204.60   $204.60  
  Purchase #6 $181.68   11.664%   $202.8712   $202.87   $202.85   $202.90  
  Purchase #7 $174.83   5.179%   $183.8844   $183.88   $183.90   $183.90  
  7 purchase totals = $1,209.99       $1,301.4681   $1,301.46   $1,301.45   $1,301.40