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 $85.82   9.571%   $94.0338   $94.03   $94.05   $94.00  
  Purchase #2 $232.65   6.288%   $247.279   $247.28   $247.30   $247.30  
  Purchase #3 $189.41   7.185%   $203.0191   $203.02   $203.00   $203.00  
  Purchase #4 $202.31   8.267%   $219.035   $219.04   $219.05   $219.00  
  Purchase #5 $65.48   10.592%   $72.4156   $72.42   $72.40   $72.40  
  Purchase #6 $77.26   12.492%   $86.9113   $86.91   $86.90   $86.90  
  Purchase #7 $28.46   6.797%   $30.3944   $30.39   $30.40   $30.40  
  7 purchase totals = $881.39       $953.0882   $953.09   $953.10   $953.00