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	$11.88	5.774%	$12.566	$12.57	$12.55	$12.60
Purchase #2	$33.32	7.139%	$35.6987	$35.70	$35.70	$35.70
Purchase #3	$19.66	4.306%	$20.5066	$20.51	$20.50	$20.50
Purchase #4	$50.31	7.617%	$54.1421	$54.14	$54.15	$54.10
Purchase #5	$224.68	13.567%	$255.1623	$255.16	$255.15	$255.20
Purchase #6	$202.40	4.554%	$211.6173	$211.62	$211.60	$211.60
Purchase #7	$211.80	5.635%	$223.7349	$223.73	$223.75	$223.70
7 purchase totals =	$754.05		$813.4279	$813.43	$813.40	$813.40