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 $68.33   8.245%   $73.9638   $73.96   $73.95   $74.00  
  Purchase #2 $211.67   11.494%   $235.9993   $236.00   $236.00   $236.00  
  Purchase #3 $216.31   13.445%   $245.3929   $245.39   $245.40   $245.40  
  Purchase #4 $243.35   5.531%   $256.8097   $256.81   $256.80   $256.80  
  Purchase #5 $154.32   13.212%   $174.7088   $174.71   $174.70   $174.70  
  Purchase #6 $197.77   4.682%   $207.0296   $207.03   $207.05   $207.00  
  Purchase #7 $142.51   9.866%   $156.57   $156.57   $156.55   $156.60  
  7 purchase totals = $1,234.26       $1,350.4741   $1,350.47   $1,350.45   $1,350.50