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	$62.28	4.625%	$65.1605	$65.16	$65.15	$65.20
Purchase #2	$33.30	13.589%	$37.8251	$37.83	$37.85	$37.80
Purchase #3	$91.76	13.847%	$104.466	$104.47	$104.45	$104.50
Purchase #4	$232.41	8.109%	$251.2561	$251.26	$251.25	$251.30
Purchase #5	$225.38	11.313%	$250.8772	$250.88	$250.90	$250.90
Purchase #6	$229.69	6.364%	$244.3075	$244.31	$244.30	$244.30
Purchase #7	$176.49	6.683%	$188.2848	$188.28	$188.30	$188.30
7 purchase totals =	$1,051.31		$1,142.1772	$1,142.19	$1,142.20	$1,142.30