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 $181.29   7.564%   $195.0028   $195.00   $195.00   $195.00  
  Purchase #2 $198.39   3.326%   $204.9885   $204.99   $205.00   $205.00  
  Purchase #3 $31.46   13.516%   $35.7121   $35.71   $35.70   $35.70  
  Purchase #4 $89.25   6.810%   $95.3279   $95.33   $95.35   $95.30  
  Purchase #5 $25.30   6.752%   $27.0083   $27.01   $27.00   $27.00  
  Purchase #6 $152.85   13.738%   $173.8485   $173.85   $173.85   $173.80  
  Purchase #7 $153.61   10.717%   $170.0724   $170.07   $170.05   $170.10  
  7 purchase totals = $832.15       $901.9605   $901.96   $901.95   $901.90