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 $92.44   3.154%   $95.3556   $95.36   $95.35   $95.40  
  Purchase #2 $104.84   4.170%   $109.2118   $109.21   $109.20   $109.20  
  Purchase #3 $109.59   9.766%   $120.2926   $120.29   $120.30   $120.30  
  Purchase #4 $198.48   9.867%   $218.064   $218.06   $218.05   $218.10  
  Purchase #5 $149.76   9.781%   $164.408   $164.41   $164.40   $164.40  
  Purchase #6 $229.58   7.134%   $245.9582   $245.96   $245.95   $246.00  
  Purchase #7 $177.30   11.135%   $197.0424   $197.04   $197.05   $197.00  
  7 purchase totals = $1,061.99       $1,150.3326   $1,150.33   $1,150.30   $1,150.40