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 $32.39   4.810%   $33.948   $33.95   $33.95   $33.90  
  Purchase #2 $101.41   8.424%   $109.9528   $109.95   $109.95   $110.00  
  Purchase #3 $161.74   9.829%   $177.6374   $177.64   $177.65   $177.60  
  Purchase #4 $187.58   8.617%   $203.7438   $203.74   $203.75   $203.70  
  Purchase #5 $99.66   9.597%   $109.2244   $109.22   $109.20   $109.20  
  Purchase #6 $244.35   7.842%   $263.5119   $263.51   $263.50   $263.50  
  Purchase #7 $109.88   6.364%   $116.8728   $116.87   $116.85   $116.90  
  7 purchase totals = $937.01       $1,014.8911   $1,014.88   $1,014.85   $1,014.80