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	$112.28	4.353%	$117.1675	$117.17	$117.15	$117.20
Purchase #2	$135.40	4.196%	$141.0814	$141.08	$141.10	$141.10
Purchase #3	$235.51	8.534%	$255.6084	$255.61	$255.60	$255.60
Purchase #4	$71.70	13.746%	$81.5559	$81.56	$81.55	$81.60
Purchase #5	$199.29	12.231%	$223.6652	$223.67	$223.65	$223.70
Purchase #6	$41.26	9.615%	$45.2271	$45.23	$45.25	$45.20
Purchase #7	$183.30	7.694%	$197.4031	$197.40	$197.40	$197.40
7 purchase totals =	$978.74		$1,061.7086	$1,061.72	$1,061.70	$1,061.80