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	$177.48	4.191%	$184.9182	$184.92	$184.90	$184.90
Purchase #2	$56.53	13.785%	$64.3227	$64.32	$64.30	$64.30
Purchase #3	$240.78	6.307%	$255.966	$255.97	$255.95	$256.00
Purchase #4	$156.74	3.427%	$162.1115	$162.11	$162.10	$162.10
Purchase #5	$50.89	7.445%	$54.6788	$54.68	$54.70	$54.70
Purchase #6	$191.52	13.565%	$217.4997	$217.50	$217.50	$217.50
Purchase #7	$191.72	4.613%	$200.564	$200.56	$200.55	$200.60
7 purchase totals =	$1,065.66		$1,140.0609	$1,140.06	$1,140.00	$1,140.10