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 $88.93   8.236%   $96.2543   $96.25   $96.25   $96.30  
  Purchase #2 $94.44   13.543%   $107.23   $107.23   $107.25   $107.20  
  Purchase #3 $195.74   10.695%   $216.6744   $216.67   $216.65   $216.70  
  Purchase #4 $219.54   12.166%   $246.2492   $246.25   $246.25   $246.20  
  Purchase #5 $85.53   7.155%   $91.6497   $91.65   $91.65   $91.60  
  Purchase #6 $121.64   5.555%   $128.3971   $128.40   $128.40   $128.40  
  Purchase #7 $247.50   13.819%   $281.702   $281.70   $281.70   $281.70  
  7 purchase totals = $1,053.32       $1,168.1567   $1,168.15   $1,168.15   $1,168.10