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	$202.50	11.435%	$225.6559	$225.66	$225.65	$225.70
Purchase #2	$99.57	13.300%	$112.8128	$112.81	$112.80	$112.80
Purchase #3	$58.90	9.163%	$64.297	$64.30	$64.30	$64.30
Purchase #4	$54.94	10.333%	$60.617	$60.62	$60.60	$60.60
Purchase #5	$20.36	12.341%	$22.8726	$22.87	$22.85	$22.90
Purchase #6	$29.61	9.495%	$32.4215	$32.42	$32.40	$32.40
Purchase #7	$89.85	6.721%	$95.8888	$95.89	$95.90	$95.90
7 purchase totals =	$555.73		$614.5656	$614.57	$614.50	$614.60