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	$106.92	5.416%	$112.7108	$112.71	$112.70	$112.70
Purchase #2	$168.42	13.565%	$191.2662	$191.27	$191.25	$191.30
Purchase #3	$34.64	5.719%	$36.6211	$36.62	$36.60	$36.60
Purchase #4	$34.44	10.315%	$37.9925	$37.99	$38.00	$38.00
Purchase #5	$175.37	9.257%	$191.604	$191.60	$191.60	$191.60
Purchase #6	$206.41	7.784%	$222.477	$222.48	$222.50	$222.50
Purchase #7	$108.28	3.199%	$111.7439	$111.74	$111.75	$111.70
7 purchase totals =	$834.48		$904.4155	$904.41	$904.40	$904.40