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	$68.63	3.228%	$70.8454	$70.85	$70.85	$70.80
Purchase #2	$113.87	4.730%	$119.2561	$119.26	$119.25	$119.30
Purchase #3	$35.58	12.218%	$39.9272	$39.93	$39.95	$39.90
Purchase #4	$32.81	8.694%	$35.6625	$35.66	$35.65	$35.70
Purchase #5	$165.37	4.521%	$172.8464	$172.85	$172.85	$172.80
Purchase #6	$181.51	10.364%	$200.3217	$200.32	$200.30	$200.30
Purchase #7	$98.94	9.621%	$108.459	$108.46	$108.45	$108.50
7 purchase totals =	$696.71		$747.3183	$747.33	$747.30	$747.30