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	$191.75	6.717%	$204.6298	$204.63	$204.65	$204.60
Purchase #2	$62.48	4.784%	$65.469	$65.47	$65.45	$65.50
Purchase #3	$80.69	9.243%	$88.1482	$88.15	$88.15	$88.10
Purchase #4	$63.66	5.798%	$67.351	$67.35	$67.35	$67.40
Purchase #5	$208.64	7.136%	$223.5286	$223.53	$223.55	$223.50
Purchase #6	$37.91	10.851%	$42.0236	$42.02	$42.00	$42.00
Purchase #7	$215.72	3.612%	$223.5118	$223.51	$223.50	$223.50
7 purchase totals =	$860.85		$914.6620	$914.66	$914.65	$914.60