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 $214.98   8.199%   $232.6062   $232.61   $232.60   $232.60  
  Purchase #2 $174.60   4.414%   $182.3068   $182.31   $182.30   $182.30  
  Purchase #3 $208.53   11.561%   $232.6382   $232.64   $232.65   $232.60  
  Purchase #4 $68.36   12.424%   $76.853   $76.85   $76.85   $76.90  
  Purchase #5 $11.86   10.235%   $13.0739   $13.07   $13.05   $13.10  
  Purchase #6 $204.27   7.118%   $218.8099   $218.81   $218.80   $218.80  
  Purchase #7 $59.25   12.419%   $66.6083   $66.61   $66.60   $66.60  
  7 purchase totals = $941.85       $1,022.8963   $1,022.90   $1,022.85   $1,022.90