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	$166.84	3.472%	$172.6327	$172.63	$172.65	$172.60
Purchase #2	$51.43	11.732%	$57.4638	$57.46	$57.45	$57.50
Purchase #3	$175.31	13.584%	$199.1241	$199.12	$199.10	$199.10
Purchase #4	$246.29	7.309%	$264.2913	$264.29	$264.30	$264.30
Purchase #5	$94.74	9.783%	$104.0084	$104.01	$104.00	$104.00
Purchase #6	$113.57	13.539%	$128.9462	$128.95	$128.95	$128.90
Purchase #7	$49.33	10.708%	$54.6123	$54.61	$54.60	$54.60
7 purchase totals =	$897.51		$981.0788	$981.07	$981.05	$981.00