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	$235.43	6.499%	$250.7306	$250.73	$250.75	$250.70
Purchase #2	$14.92	6.326%	$15.8638	$15.86	$15.85	$15.90
Purchase #3	$187.79	11.295%	$209.0009	$209.00	$209.00	$209.00
Purchase #4	$246.70	9.150%	$269.2731	$269.27	$269.25	$269.30
Purchase #5	$129.73	13.128%	$146.761	$146.76	$146.75	$146.80
Purchase #6	$99.38	12.501%	$111.8035	$111.80	$111.80	$111.80
Purchase #7	$66.51	11.796%	$74.3555	$74.36	$74.35	$74.40
7 purchase totals =	$980.46		$1,077.7884	$1,077.78	$1,077.75	$1,077.90