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	$165.30	4.320%	$172.441	$172.44	$172.45	$172.40
Purchase #2	$238.92	3.494%	$247.2679	$247.27	$247.25	$247.30
Purchase #3	$66.93	10.149%	$73.7227	$73.72	$73.70	$73.70
Purchase #4	$91.62	11.196%	$101.8778	$101.88	$101.90	$101.90
Purchase #5	$145.52	13.326%	$164.912	$164.91	$164.90	$164.90
Purchase #6	$25.27	12.384%	$28.3994	$28.40	$28.40	$28.40
Purchase #7	$57.66	13.791%	$65.6119	$65.61	$65.60	$65.60
7 purchase totals =	$791.22		$854.2327	$854.23	$854.20	$854.20