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 $54.52   11.350%   $60.708   $60.71   $60.70   $60.70  
  Purchase #2 $64.68   4.771%   $67.7659   $67.77   $67.75   $67.80  
  Purchase #3 $198.63   3.629%   $205.8383   $205.84   $205.85   $205.80  
  Purchase #4 $158.68   11.847%   $177.4788   $177.48   $177.50   $177.50  
  Purchase #5 $87.57   6.572%   $93.3251   $93.33   $93.35   $93.30  
  Purchase #6 $87.58   10.705%   $96.9554   $96.96   $96.95   $97.00  
  Purchase #7 $222.95   9.739%   $244.6631   $244.66   $244.65   $244.70  
  7 purchase totals = $874.61       $946.7346   $946.75   $946.75   $946.80