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 $196.38   11.666%   $219.2897   $219.29   $219.30   $219.30  
  Purchase #2 $212.95   11.500%   $237.4393   $237.44   $237.45   $237.40  
  Purchase #3 $11.92   10.620%   $13.1859   $13.19   $13.20   $13.20  
  Purchase #4 $148.46   13.132%   $167.9558   $167.96   $167.95   $168.00  
  Purchase #5 $66.99   5.399%   $70.6068   $70.61   $70.60   $70.60  
  Purchase #6 $214.81   11.623%   $239.7774   $239.78   $239.80   $239.80  
  Purchase #7 $103.60   9.217%   $113.1488   $113.15   $113.15   $113.10  
  7 purchase totals = $955.11       $1,061.4037   $1,061.42   $1,061.45   $1,061.40