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 $191.48   7.665%   $206.1569   $206.16   $206.15   $206.20  
  Purchase #2 $243.48   9.383%   $266.3257   $266.33   $266.35   $266.30  
  Purchase #3 $209.97   13.701%   $238.738   $238.74   $238.75   $238.70  
  Purchase #4 $129.26   6.424%   $137.5637   $137.56   $137.55   $137.60  
  Purchase #5 $165.82   12.764%   $186.9853   $186.99   $187.00   $187.00  
  Purchase #6 $173.79   8.580%   $188.7012   $188.70   $188.70   $188.70  
  Purchase #7 $87.44   11.775%   $97.7361   $97.74   $97.75   $97.70  
  7 purchase totals = $1,201.24       $1,322.2069   $1,322.22   $1,322.25   $1,322.20