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 $93.39   5.297%   $98.3369   $98.34   $98.35   $98.30  
  Purchase #2 $198.46   7.160%   $212.6697   $212.67   $212.65   $212.70  
  Purchase #3 $213.50   8.735%   $232.1492   $232.15   $232.15   $232.10  
  Purchase #4 $83.86   5.227%   $88.2434   $88.24   $88.25   $88.20  
  Purchase #5 $94.98   12.596%   $106.9437   $106.94   $106.95   $106.90  
  Purchase #6 $181.54   8.693%   $197.3213   $197.32   $197.30   $197.30  
  Purchase #7 $147.45   8.815%   $160.4477   $160.45   $160.45   $160.40  
  7 purchase totals = $1,013.18       $1,096.1119   $1,096.11   $1,096.10   $1,095.90