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	$196.50	11.287%	$218.679	$218.68	$218.70	$218.70
Purchase #2	$46.38	8.644%	$50.3891	$50.39	$50.40	$50.40
Purchase #3	$181.26	7.230%	$194.3651	$194.37	$194.35	$194.40
Purchase #4	$131.83	3.256%	$136.1224	$136.12	$136.10	$136.10
Purchase #5	$250.82	9.233%	$273.9782	$273.98	$274.00	$274.00
Purchase #6	$37.33	5.794%	$39.4929	$39.49	$39.50	$39.50
Purchase #7	$33.77	10.122%	$37.1882	$37.19	$37.20	$37.20
7 purchase totals =	$877.89		$950.2149	$950.22	$950.25	$950.30