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	$34.78	6.774%	$37.136	$37.14	$37.15	$37.10
Purchase #2	$162.61	3.659%	$168.5599	$168.56	$168.55	$168.60
Purchase #3	$178.67	10.491%	$197.4143	$197.41	$197.40	$197.40
Purchase #4	$52.56	10.688%	$58.1776	$58.18	$58.20	$58.20
Purchase #5	$131.49	11.519%	$146.6363	$146.64	$146.65	$146.60
Purchase #6	$204.72	12.116%	$229.5239	$229.52	$229.50	$229.50
Purchase #7	$223.36	12.174%	$250.5518	$250.55	$250.55	$250.60
7 purchase totals =	$988.19		$1,087.9998	$1,088.00	$1,088.00	$1,088.00