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 $70.67   8.594%   $76.7434   $76.74   $76.75   $76.70  
  Purchase #2 $188.47   10.217%   $207.726   $207.73   $207.75   $207.70  
  Purchase #3 $208.94   5.279%   $219.9699   $219.97   $219.95   $220.00  
  Purchase #4 $248.66   11.204%   $276.5199   $276.52   $276.50   $276.50  
  Purchase #5 $6.50   11.777%   $7.2655   $7.27   $7.25   $7.30  
  Purchase #6 $232.84   10.227%   $256.6525   $256.65   $256.65   $256.70  
  Purchase #7 $145.95   11.768%   $163.1254   $163.13   $163.15   $163.10  
  7 purchase totals = $1,102.03       $1,208.0026   $1,208.01   $1,208.00   $1,208.00