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 $67.94   11.798%   $75.9556   $75.96   $75.95   $76.00  
  Purchase #2 $147.26   3.505%   $152.4215   $152.42   $152.40   $152.40  
  Purchase #3 $107.89   7.559%   $116.0454   $116.05   $116.05   $116.00  
  Purchase #4 $184.97   11.376%   $206.0122   $206.01   $206.00   $206.00  
  Purchase #5 $202.77   13.582%   $230.3102   $230.31   $230.30   $230.30  
  Purchase #6 $110.57   7.555%   $118.9236   $118.92   $118.90   $118.90  
  Purchase #7 $201.38   7.486%   $216.4553   $216.46   $216.45   $216.50  
  7 purchase totals = $1,022.78       $1,116.1238   $1,116.13   $1,116.05   $1,116.10