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	$150.74	13.513%	$171.1095	$171.11	$171.10	$171.10
Purchase #2	$150.66	5.209%	$158.5079	$158.51	$158.50	$158.50
Purchase #3	$91.62	13.585%	$104.0666	$104.07	$104.05	$104.10
Purchase #4	$159.30	4.834%	$167.0006	$167.00	$167.00	$167.00
Purchase #5	$195.81	11.467%	$218.2635	$218.26	$218.25	$218.30
Purchase #6	$176.37	8.107%	$190.6683	$190.67	$190.65	$190.70
Purchase #7	$139.46	13.819%	$158.732	$158.73	$158.75	$158.70
7 purchase totals =	$1,063.96		$1,168.3484	$1,168.35	$1,168.30	$1,168.40