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 $197.96   3.873%   $205.627   $205.63   $205.65   $205.60  
  Purchase #2 $188.35   12.717%   $212.3025   $212.30   $212.30   $212.30  
  Purchase #3 $197.54   5.684%   $208.7682   $208.77   $208.75   $208.80  
  Purchase #4 $62.61   12.294%   $70.3073   $70.31   $70.30   $70.30  
  Purchase #5 $152.74   6.584%   $162.7964   $162.80   $162.80   $162.80  
  Purchase #6 $219.60   11.112%   $244.002   $244.00   $244.00   $244.00  
  Purchase #7 $220.92   5.827%   $233.793   $233.79   $233.80   $233.80  
  7 purchase totals = $1,239.72       $1,337.5964   $1,337.60   $1,337.60   $1,337.60