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	$54.67	13.707%	$62.1636	$62.16	$62.15	$62.20
Purchase #2	$112.88	9.191%	$123.2548	$123.25	$123.25	$123.30
Purchase #3	$6.42	11.665%	$7.1689	$7.17	$7.15	$7.20
Purchase #4	$163.95	8.804%	$178.3842	$178.38	$178.40	$178.40
Purchase #5	$35.30	6.608%	$37.6326	$37.63	$37.65	$37.60
Purchase #6	$131.42	9.192%	$143.5001	$143.50	$143.50	$143.50
Purchase #7	$94.93	4.549%	$99.2484	$99.25	$99.25	$99.20
7 purchase totals =	$599.57		$651.3526	$651.34	$651.35	$651.40