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 $84.33   5.129%   $88.6553   $88.66   $88.65   $88.70  
  Purchase #2 $41.49   8.297%   $44.9324   $44.93   $44.95   $44.90  
  Purchase #3 $248.87   5.846%   $263.4189   $263.42   $263.40   $263.40  
  Purchase #4 $203.49   6.400%   $216.5134   $216.51   $216.50   $216.50  
  Purchase #5 $212.59   7.223%   $227.9454   $227.95   $227.95   $227.90  
  Purchase #6 $54.73   9.606%   $59.9874   $59.99   $60.00   $60.00  
  Purchase #7 $124.75   5.503%   $131.615   $131.62   $131.60   $131.60  
  7 purchase totals = $970.25       $1,033.0678   $1,033.08   $1,033.05   $1,033.00