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 $194.82   11.225%   $216.6885   $216.69   $216.70   $216.70  
  Purchase #2 $203.74   10.353%   $224.8332   $224.83   $224.85   $224.80  
  Purchase #3 $189.62   11.776%   $211.9497   $211.95   $211.95   $211.90  
  Purchase #4 $38.96   7.548%   $41.9007   $41.90   $41.90   $41.90  
  Purchase #5 $91.97   5.300%   $96.8444   $96.84   $96.85   $96.80  
  Purchase #6 $179.65   11.792%   $200.8343   $200.83   $200.85   $200.80  
  Purchase #7 $68.90   10.795%   $76.3378   $76.34   $76.35   $76.30  
  7 purchase totals = $967.66       $1,069.3886   $1,069.38   $1,069.45   $1,069.20