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 $195.65   5.419%   $206.2523   $206.25   $206.25   $206.30  
  Purchase #2 $51.75   13.392%   $58.6804   $58.68   $58.70   $58.70  
  Purchase #3 $243.79   9.829%   $267.7521   $267.75   $267.75   $267.80  
  Purchase #4 $160.65   4.272%   $167.513   $167.51   $167.50   $167.50  
  Purchase #5 $77.94   10.177%   $85.872   $85.87   $85.85   $85.90  
  Purchase #6 $211.48   6.599%   $225.4356   $225.44   $225.45   $225.40  
  Purchase #7 $93.38   9.424%   $102.1801   $102.18   $102.20   $102.20  
  7 purchase totals = $1,034.64       $1,113.6855   $1,113.68   $1,113.70   $1,113.80