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 $32.29   8.258%   $34.9565   $34.96   $34.95   $35.00  
  Purchase #2 $121.96   3.538%   $126.2749   $126.27   $126.25   $126.30  
  Purchase #3 $199.49   8.736%   $216.9174   $216.92   $216.90   $216.90  
  Purchase #4 $214.86   13.370%   $243.5868   $243.59   $243.60   $243.60  
  Purchase #5 $44.94   3.727%   $46.6149   $46.61   $46.60   $46.60  
  Purchase #6 $153.46   9.527%   $168.0801   $168.08   $168.10   $168.10  
  Purchase #7 $190.38   10.753%   $210.8516   $210.85   $210.85   $210.90  
  7 purchase totals = $957.38       $1,047.2822   $1,047.28   $1,047.25   $1,047.40