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	$215.45	3.809%	$223.6565	$223.66	$223.65	$223.70
Purchase #2	$175.96	8.635%	$191.1541	$191.15	$191.15	$191.20
Purchase #3	$163.74	9.556%	$179.387	$179.39	$179.40	$179.40
Purchase #4	$40.26	8.673%	$43.7517	$43.75	$43.75	$43.80
Purchase #5	$187.76	13.114%	$212.3828	$212.38	$212.40	$212.40
Purchase #6	$40.91	6.799%	$43.6915	$43.69	$43.70	$43.70
Purchase #7	$179.85	6.160%	$190.9288	$190.93	$190.95	$190.90
7 purchase totals =	$1,003.93		$1,084.9524	$1,084.95	$1,085.00	$1,085.10