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 $187.69   8.143%   $202.9736   $202.97   $202.95   $203.00  
  Purchase #2 $203.38   4.234%   $211.9911   $211.99   $212.00   $212.00  
  Purchase #3 $204.36   4.738%   $214.0426   $214.04   $214.05   $214.00  
  Purchase #4 $159.40   4.774%   $167.0098   $167.01   $167.00   $167.00  
  Purchase #5 $46.45   9.250%   $50.7466   $50.75   $50.75   $50.70  
  Purchase #6 $199.77   3.196%   $206.1546   $206.15   $206.15   $206.20  
  Purchase #7 $62.90   4.707%   $65.8607   $65.86   $65.85   $65.90  
  7 purchase totals = $1,063.95       $1,118.7790   $1,118.77   $1,118.75   $1,118.80