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 $195.57   7.178%   $209.608   $209.61   $209.60   $209.60  
  Purchase #2 $66.30   13.338%   $75.1431   $75.14   $75.15   $75.10  
  Purchase #3 $56.82   8.662%   $61.7417   $61.74   $61.75   $61.70  
  Purchase #4 $205.69   11.375%   $229.0872   $229.09   $229.10   $229.10  
  Purchase #5 $187.74   11.725%   $209.7525   $209.75   $209.75   $209.80  
  Purchase #6 $37.34   9.764%   $40.9859   $40.99   $41.00   $41.00  
  Purchase #7 $174.52   6.207%   $185.3525   $185.35   $185.35   $185.40  
  7 purchase totals = $923.98       $1,011.6709   $1,011.67   $1,011.70   $1,011.70