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	$158.76	6.108%	$168.4571	$168.46	$168.45	$168.50
Purchase #2	$232.85	5.173%	$244.8953	$244.90	$244.90	$244.90
Purchase #3	$209.88	6.607%	$223.7468	$223.75	$223.75	$223.70
Purchase #4	$26.42	3.283%	$27.2874	$27.29	$27.30	$27.30
Purchase #5	$190.83	4.846%	$200.0776	$200.08	$200.10	$200.10
Purchase #6	$220.45	5.196%	$231.9046	$231.90	$231.90	$231.90
Purchase #7	$112.51	8.634%	$122.2241	$122.22	$122.20	$122.20
7 purchase totals =	$1,151.70		$1,218.5929	$1,218.60	$1,218.60	$1,218.60