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 $206.46   4.731%   $216.2276   $216.23   $216.25   $216.20  
  Purchase #2 $70.97   6.104%   $75.302   $75.30   $75.30   $75.30  
  Purchase #3 $23.29   3.293%   $24.0569   $24.06   $24.05   $24.10  
  Purchase #4 $238.38   8.759%   $259.2597   $259.26   $259.25   $259.30  
  Purchase #5 $206.42   3.292%   $213.2153   $213.22   $213.20   $213.20  
  Purchase #6 $85.89   13.797%   $97.7402   $97.74   $97.75   $97.70  
  Purchase #7 $160.67   10.771%   $177.9758   $177.98   $178.00   $178.00  
  7 purchase totals = $992.08       $1,063.7775   $1,063.79   $1,063.80   $1,063.80