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 $153.56   7.578%   $165.1968   $165.20   $165.20   $165.20  
  Purchase #2 $171.86   13.553%   $195.1522   $195.15   $195.15   $195.20  
  Purchase #3 $86.36   11.288%   $96.1083   $96.11   $96.10   $96.10  
  Purchase #4 $118.49   7.590%   $127.4834   $127.48   $127.50   $127.50  
  Purchase #5 $125.94   4.558%   $131.6803   $131.68   $131.70   $131.70  
  Purchase #6 $118.50   10.145%   $130.5218   $130.52   $130.50   $130.50  
  Purchase #7 $82.52   7.380%   $88.61   $88.61   $88.60   $88.60  
  7 purchase totals = $857.23       $934.7528   $934.75   $934.75   $934.80