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	$179.65	7.103%	$192.4105	$192.41	$192.40	$192.40
Purchase #2	$140.39	4.252%	$146.3594	$146.36	$146.35	$146.40
Purchase #3	$89.86	10.174%	$99.0024	$99.00	$99.00	$99.00
Purchase #4	$194.76	5.309%	$205.0998	$205.10	$205.10	$205.10
Purchase #5	$165.65	10.152%	$182.4668	$182.47	$182.45	$182.50
Purchase #6	$245.94	10.447%	$271.6334	$271.63	$271.65	$271.60
Purchase #7	$57.59	13.187%	$65.1844	$65.18	$65.20	$65.20
7 purchase totals =	$1,073.84		$1,162.1567	$1,162.15	$1,162.15	$1,162.20