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 $94.85   9.757%   $104.1045   $104.10   $104.10   $104.10  
  Purchase #2 $85.47   12.448%   $96.1093   $96.11   $96.10   $96.10  
  Purchase #3 $101.51   5.401%   $106.9926   $106.99   $107.00   $107.00  
  Purchase #4 $231.29   5.446%   $243.8861   $243.89   $243.90   $243.90  
  Purchase #5 $161.75   6.243%   $171.8481   $171.85   $171.85   $171.80  
  Purchase #6 $236.59   8.474%   $256.6386   $256.64   $256.65   $256.60  
  Purchase #7 $167.80   13.601%   $190.6225   $190.62   $190.60   $190.60  
  7 purchase totals = $1,079.26       $1,170.2017   $1,170.20   $1,170.20   $1,170.10