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	$77.66	12.142%	$87.0895	$87.09	$87.10	$87.10
Purchase #2	$94.73	6.466%	$100.8552	$100.86	$100.85	$100.90
Purchase #3	$212.88	3.759%	$220.8822	$220.88	$220.90	$220.90
Purchase #4	$144.69	4.647%	$151.4137	$151.41	$151.40	$151.40
Purchase #5	$225.76	5.817%	$238.8925	$238.89	$238.90	$238.90
Purchase #6	$113.26	3.428%	$117.1426	$117.14	$117.15	$117.10
Purchase #7	$201.84	10.718%	$223.4732	$223.47	$223.45	$223.50
7 purchase totals =	$1,070.82		$1,139.7489	$1,139.74	$1,139.75	$1,139.80