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	$56.69	3.124%	$58.461	$58.46	$58.45	$58.50
Purchase #2	$12.83	12.115%	$14.3844	$14.38	$14.40	$14.40
Purchase #3	$152.70	8.565%	$165.7788	$165.78	$165.80	$165.80
Purchase #4	$53.41	4.575%	$55.8535	$55.85	$55.85	$55.90
Purchase #5	$93.29	10.453%	$103.0416	$103.04	$103.05	$103.00
Purchase #6	$38.60	4.180%	$40.2135	$40.21	$40.20	$40.20
Purchase #7	$120.50	8.271%	$130.4666	$130.47	$130.45	$130.50
7 purchase totals =	$528.02		$568.1994	$568.19	$568.20	$568.30