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 $167.49   8.638%   $181.9578   $181.96   $181.95   $182.00  
  Purchase #2 $70.53   4.716%   $73.8562   $73.86   $73.85   $73.90  
  Purchase #3 $170.40   8.544%   $184.959   $184.96   $184.95   $185.00  
  Purchase #4 $133.80   4.268%   $139.5106   $139.51   $139.50   $139.50  
  Purchase #5 $114.48   4.117%   $119.1931   $119.19   $119.20   $119.20  
  Purchase #6 $201.72   8.623%   $219.1143   $219.11   $219.10   $219.10  
  Purchase #7 $162.59   8.209%   $175.937   $175.94   $175.95   $175.90  
  7 purchase totals = $1,021.01       $1,094.5280   $1,094.53   $1,094.50   $1,094.60