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 $95.42   3.404%   $98.6681   $98.67   $98.65   $98.70  
  Purchase #2 $12.84   12.402%   $14.4324   $14.43   $14.45   $14.40  
  Purchase #3 $225.82   7.728%   $243.2714   $243.27   $243.25   $243.30  
  Purchase #4 $91.49   12.518%   $102.9427   $102.94   $102.95   $102.90  
  Purchase #5 $154.61   8.180%   $167.2571   $167.26   $167.25   $167.30  
  Purchase #6 $153.93   3.501%   $159.3191   $159.32   $159.30   $159.30  
  Purchase #7 $213.48   12.823%   $240.8545   $240.85   $240.85   $240.90  
  7 purchase totals = $947.59       $1,026.7453   $1,026.74   $1,026.70   $1,026.80