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	$54.99	12.237%	$61.7191	$61.72	$61.70	$61.70
Purchase #2	$55.46	6.502%	$59.066	$59.07	$59.05	$59.10
Purchase #3	$184.52	4.153%	$192.1831	$192.18	$192.20	$192.20
Purchase #4	$123.83	13.407%	$140.4319	$140.43	$140.45	$140.40
Purchase #5	$209.69	13.581%	$238.168	$238.17	$238.15	$238.20
Purchase #6	$194.60	6.158%	$206.5835	$206.58	$206.60	$206.60
Purchase #7	$65.83	8.854%	$71.6586	$71.66	$71.65	$71.70
7 purchase totals =	$888.92		$969.8102	$969.81	$969.80	$969.90