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	$185.68	12.627%	$209.1258	$209.13	$209.15	$209.10
Purchase #2	$137.30	6.110%	$145.689	$145.69	$145.70	$145.70
Purchase #3	$235.28	7.295%	$252.4437	$252.44	$252.45	$252.40
Purchase #4	$167.88	13.824%	$191.0877	$191.09	$191.10	$191.10
Purchase #5	$150.98	5.420%	$159.1631	$159.16	$159.15	$159.20
Purchase #6	$80.48	12.423%	$90.478	$90.48	$90.50	$90.50
Purchase #7	$11.48	8.532%	$12.4595	$12.46	$12.45	$12.50
7 purchase totals =	$969.08		$1,060.4468	$1,060.45	$1,060.50	$1,060.50