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	$47.28	9.190%	$51.625	$51.63	$51.65	$51.60
Purchase #2	$64.73	11.339%	$72.0697	$72.07	$72.05	$72.10
Purchase #3	$161.96	6.606%	$172.6591	$172.66	$172.65	$172.70
Purchase #4	$234.96	7.535%	$252.6642	$252.66	$252.65	$252.70
Purchase #5	$99.84	9.311%	$109.1361	$109.14	$109.15	$109.10
Purchase #6	$98.45	13.528%	$111.7683	$111.77	$111.75	$111.80
Purchase #7	$202.57	6.429%	$215.5932	$215.59	$215.60	$215.60
7 purchase totals =	$909.79		$985.5156	$985.52	$985.50	$985.60