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	$238.58	6.511%	$254.1139	$254.11	$254.10	$254.10
Purchase #2	$85.51	6.343%	$90.9339	$90.93	$90.95	$90.90
Purchase #3	$100.62	4.809%	$105.4588	$105.46	$105.45	$105.50
Purchase #4	$244.46	10.179%	$269.3436	$269.34	$269.35	$269.30
Purchase #5	$180.34	5.495%	$190.2497	$190.25	$190.25	$190.20
Purchase #6	$35.36	6.792%	$37.7617	$37.76	$37.75	$37.80
Purchase #7	$99.60	8.683%	$108.2483	$108.25	$108.25	$108.20
7 purchase totals =	$984.47		$1,056.1099	$1,056.10	$1,056.10	$1,056.00