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	$178.90	3.553%	$185.2563	$185.26	$185.25	$185.30
Purchase #2	$105.78	3.634%	$109.624	$109.62	$109.60	$109.60
Purchase #3	$152.95	4.314%	$159.5483	$159.55	$159.55	$159.50
Purchase #4	$52.37	5.227%	$55.1074	$55.11	$55.10	$55.10
Purchase #5	$197.39	7.152%	$211.5073	$211.51	$211.50	$211.50
Purchase #6	$195.74	6.410%	$208.2869	$208.29	$208.30	$208.30
Purchase #7	$12.62	8.261%	$13.6625	$13.66	$13.65	$13.70
7 purchase totals =	$895.75		$942.9927	$943.00	$942.95	$943.00