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 $147.36   11.297%   $164.0073   $164.01   $164.00   $164.00  
  Purchase #2 $162.58   7.323%   $174.4857   $174.49   $174.50   $174.50  
  Purchase #3 $179.60   3.747%   $186.3296   $186.33   $186.35   $186.30  
  Purchase #4 $162.97   9.790%   $178.9248   $178.92   $178.90   $178.90  
  Purchase #5 $5.67   9.290%   $6.1967   $6.20   $6.20   $6.20  
  Purchase #6 $231.73   11.319%   $257.9595   $257.96   $257.95   $258.00  
  Purchase #7 $60.98   8.719%   $66.2968   $66.30   $66.30   $66.30  
  7 purchase totals = $950.89       $1,034.2004   $1,034.21   $1,034.20   $1,034.20