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 $30.88   4.721%   $32.3378   $32.34   $32.35   $32.30  
  Purchase #2 $105.62   12.275%   $118.5849   $118.58   $118.60   $118.60  
  Purchase #3 $241.51   10.565%   $267.0255   $267.03   $267.05   $267.00  
  Purchase #4 $101.84   13.689%   $115.7809   $115.78   $115.80   $115.80  
  Purchase #5 $216.79   11.520%   $241.7642   $241.76   $241.75   $241.80  
  Purchase #6 $232.94   4.606%   $243.6692   $243.67   $243.65   $243.70  
  Purchase #7 $146.30   6.522%   $155.8417   $155.84   $155.85   $155.80  
  7 purchase totals = $1,075.88       $1,175.0042   $1,175.00   $1,175.05   $1,175.00