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	$32.87	12.759%	$37.0639	$37.06	$37.05	$37.10
Purchase #2	$64.57	7.730%	$69.5613	$69.56	$69.55	$69.60
Purchase #3	$35.79	4.282%	$37.3225	$37.32	$37.30	$37.30
Purchase #4	$204.68	8.194%	$221.4515	$221.45	$221.45	$221.50
Purchase #5	$230.85	10.678%	$255.5002	$255.50	$255.50	$255.50
Purchase #6	$169.77	13.472%	$192.6414	$192.64	$192.65	$192.60
Purchase #7	$79.36	4.806%	$83.174	$83.17	$83.15	$83.20
7 purchase totals =	$817.89		$896.7148	$896.70	$896.65	$896.80