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	$61.30	9.422%	$67.0757	$67.08	$67.10	$67.10
Purchase #2	$30.93	3.107%	$31.891	$31.89	$31.90	$31.90
Purchase #3	$210.27	11.469%	$234.3859	$234.39	$234.40	$234.40
Purchase #4	$59.83	7.175%	$64.1228	$64.12	$64.10	$64.10
Purchase #5	$167.90	13.609%	$190.7495	$190.75	$190.75	$190.70
Purchase #6	$11.33	8.700%	$12.3157	$12.32	$12.30	$12.30
Purchase #7	$164.48	4.815%	$172.3997	$172.40	$172.40	$172.40
7 purchase totals =	$706.04		$772.9403	$772.95	$772.95	$772.90