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	$98.92	13.110%	$111.8884	$111.89	$111.90	$111.90
Purchase #2	$127.89	3.386%	$132.2204	$132.22	$132.20	$132.20
Purchase #3	$229.92	12.538%	$258.7474	$258.75	$258.75	$258.70
Purchase #4	$231.28	10.152%	$254.7595	$254.76	$254.75	$254.80
Purchase #5	$95.48	7.437%	$102.5808	$102.58	$102.60	$102.60
Purchase #6	$228.96	6.777%	$244.4766	$244.48	$244.50	$244.50
Purchase #7	$63.58	9.739%	$69.7721	$69.77	$69.75	$69.80
7 purchase totals =	$1,076.03		$1,174.4452	$1,174.45	$1,174.45	$1,174.50