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	$144.88	11.434%	$161.4456	$161.45	$161.45	$161.40
Purchase #2	$60.48	10.850%	$67.0421	$67.04	$67.05	$67.00
Purchase #3	$128.82	7.221%	$138.1221	$138.12	$138.10	$138.10
Purchase #4	$61.50	6.378%	$65.4225	$65.42	$65.40	$65.40
Purchase #5	$73.46	6.843%	$78.4869	$78.49	$78.50	$78.50
Purchase #6	$33.94	6.609%	$36.1831	$36.18	$36.20	$36.20
Purchase #7	$123.74	3.658%	$128.2664	$128.27	$128.25	$128.30
7 purchase totals =	$626.82		$674.9687	$674.97	$674.95	$674.90