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 $248.41   7.691%   $267.5152   $267.52   $267.50   $267.50  
  Purchase #2 $146.71   4.546%   $153.3794   $153.38   $153.40   $153.40  
  Purchase #3 $113.95   11.432%   $126.9768   $126.98   $127.00   $127.00  
  Purchase #4 $248.93   8.625%   $270.4002   $270.40   $270.40   $270.40  
  Purchase #5 $168.42   7.644%   $181.294   $181.29   $181.30   $181.30  
  Purchase #6 $188.93   7.607%   $203.3019   $203.30   $203.30   $203.30  
  Purchase #7 $209.47   8.528%   $227.3336   $227.33   $227.35   $227.30  
  7 purchase totals = $1,324.82       $1,430.2011   $1,430.20   $1,430.25   $1,430.20