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 $118.57   5.693%   $125.3202   $125.32   $125.30   $125.30  
  Purchase #2 $88.74   11.444%   $98.8954   $98.90   $98.90   $98.90  
  Purchase #3 $169.39   10.223%   $186.7067   $186.71   $186.70   $186.70  
  Purchase #4 $138.51   4.121%   $144.218   $144.22   $144.20   $144.20  
  Purchase #5 $181.98   9.828%   $199.865   $199.87   $199.85   $199.90  
  Purchase #6 $238.80   10.462%   $263.7833   $263.78   $263.80   $263.80  
  Purchase #7 $77.34   7.285%   $82.9742   $82.97   $82.95   $83.00  
  7 purchase totals = $1,013.33       $1,101.7628   $1,101.77   $1,101.70   $1,101.80