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	$228.31	13.833%	$259.8921	$259.89	$259.90	$259.90
Purchase #2	$219.47	4.373%	$229.0674	$229.07	$229.05	$229.10
Purchase #3	$22.63	13.153%	$25.6065	$25.61	$25.60	$25.60
Purchase #4	$90.55	5.166%	$95.2278	$95.23	$95.25	$95.20
Purchase #5	$178.65	3.502%	$184.9063	$184.91	$184.90	$184.90
Purchase #6	$201.38	12.451%	$226.4538	$226.45	$226.45	$226.50
Purchase #7	$135.52	11.763%	$151.4612	$151.46	$151.45	$151.50
7 purchase totals =	$1,076.51		$1,172.6151	$1,172.62	$1,172.60	$1,172.70