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	$165.27	4.374%	$172.4989	$172.50	$172.50	$172.50
Purchase #2	$12.95	7.681%	$13.9447	$13.94	$13.95	$13.90
Purchase #3	$96.76	13.185%	$109.5178	$109.52	$109.50	$109.50
Purchase #4	$32.92	8.567%	$35.7403	$35.74	$35.75	$35.70
Purchase #5	$66.98	6.628%	$71.4194	$71.42	$71.40	$71.40
Purchase #6	$64.68	10.811%	$71.6726	$71.67	$71.65	$71.70
Purchase #7	$45.65	12.826%	$51.5051	$51.51	$51.50	$51.50
7 purchase totals =	$485.21		$526.2988	$526.30	$526.25	$526.20