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	$57.34	4.673%	$60.0195	$60.02	$60.00	$60.00
Purchase #2	$20.32	12.117%	$22.7822	$22.78	$22.80	$22.80
Purchase #3	$129.42	11.716%	$144.5828	$144.58	$144.60	$144.60
Purchase #4	$231.67	13.529%	$263.0126	$263.01	$263.00	$263.00
Purchase #5	$173.31	3.711%	$179.7415	$179.74	$179.75	$179.70
Purchase #6	$222.44	10.560%	$245.9297	$245.93	$245.95	$245.90
Purchase #7	$88.65	13.468%	$100.5894	$100.59	$100.60	$100.60
7 purchase totals =	$923.15		$1,016.6577	$1,016.65	$1,016.70	$1,016.60