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	$118.36	8.714%	$128.6739	$128.67	$128.65	$128.70
Purchase #2	$101.93	3.229%	$105.2213	$105.22	$105.20	$105.20
Purchase #3	$88.88	9.685%	$97.488	$97.49	$97.50	$97.50
Purchase #4	$153.68	7.560%	$165.2982	$165.30	$165.30	$165.30
Purchase #5	$33.65	6.782%	$35.9321	$35.93	$35.95	$35.90
Purchase #6	$247.70	4.437%	$258.6904	$258.69	$258.70	$258.70
Purchase #7	$111.90	10.465%	$123.6103	$123.61	$123.60	$123.60
7 purchase totals =	$856.10		$914.9142	$914.91	$914.90	$914.90