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	$99.55	5.543%	$105.0681	$105.07	$105.05	$105.10
Purchase #2	$18.57	10.744%	$20.5652	$20.57	$20.55	$20.60
Purchase #3	$53.75	5.126%	$56.5052	$56.51	$56.50	$56.50
Purchase #4	$210.59	3.585%	$218.1397	$218.14	$218.15	$218.10
Purchase #5	$71.72	8.170%	$77.5795	$77.58	$77.60	$77.60
Purchase #6	$206.76	4.185%	$215.4129	$215.41	$215.40	$215.40
Purchase #7	$12.25	9.853%	$13.457	$13.46	$13.45	$13.50
7 purchase totals =	$673.19		$706.7276	$706.74	$706.70	$706.80