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 $84.75   13.590%   $96.2675   $96.27   $96.25   $96.30  
  Purchase #2 $194.49   4.706%   $203.6427   $203.64   $203.65   $203.60  
  Purchase #3 $210.41   6.320%   $223.7079   $223.71   $223.70   $223.70  
  Purchase #4 $165.63   4.108%   $172.4341   $172.43   $172.45   $172.40  
  Purchase #5 $226.27   12.673%   $254.9452   $254.95   $254.95   $254.90  
  Purchase #6 $57.28   9.661%   $62.8138   $62.81   $62.80   $62.80  
  Purchase #7 $187.52   4.331%   $195.6415   $195.64   $195.65   $195.60  
  7 purchase totals = $1,126.35       $1,209.4527   $1,209.45   $1,209.45   $1,209.30