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	$229.41	11.432%	$255.6362	$255.64	$255.65	$255.60
Purchase #2	$244.38	4.791%	$256.0882	$256.09	$256.10	$256.10
Purchase #3	$142.52	5.178%	$149.8997	$149.90	$149.90	$149.90
Purchase #4	$146.48	9.841%	$160.8951	$160.90	$160.90	$160.90
Purchase #5	$91.50	4.399%	$95.5251	$95.53	$95.55	$95.50
Purchase #6	$65.46	11.720%	$73.1319	$73.13	$73.15	$73.10
Purchase #7	$95.83	4.579%	$100.2181	$100.22	$100.20	$100.20
7 purchase totals =	$1,015.58		$1,091.3943	$1,091.41	$1,091.45	$1,091.30