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 $88.95   3.488%   $92.0526   $92.05   $92.05   $92.10  
  Purchase #2 $231.72   4.282%   $241.6423   $241.64   $241.65   $241.60  
  Purchase #3 $209.88   3.834%   $217.9268   $217.93   $217.95   $217.90  
  Purchase #4 $100.96   4.674%   $105.6789   $105.68   $105.70   $105.70  
  Purchase #5 $181.49   11.288%   $201.9766   $201.98   $202.00   $202.00  
  Purchase #6 $207.80   10.772%   $230.1842   $230.18   $230.20   $230.20  
  Purchase #7 $218.66   12.110%   $245.1397   $245.14   $245.15   $245.10  
  7 purchase totals = $1,239.46       $1,334.6011   $1,334.60   $1,334.70   $1,334.60