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	$9.76	4.388%	$10.1883	$10.19	$10.20	$10.20
Purchase #2	$149.37	13.140%	$168.9972	$169.00	$169.00	$169.00
Purchase #3	$196.77	13.594%	$223.5189	$223.52	$223.50	$223.50
Purchase #4	$241.87	11.302%	$269.2061	$269.21	$269.20	$269.20
Purchase #5	$131.90	3.784%	$136.8911	$136.89	$136.90	$136.90
Purchase #6	$149.40	10.835%	$165.5875	$165.59	$165.60	$165.60
Purchase #7	$223.91	13.562%	$254.2767	$254.28	$254.30	$254.30
7 purchase totals =	$1,102.98		$1,228.6658	$1,228.68	$1,228.70	$1,228.70