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	$114.59	11.287%	$127.5238	$127.52	$127.50	$127.50
Purchase #2	$15.97	4.674%	$16.7164	$16.72	$16.70	$16.70
Purchase #3	$217.66	11.422%	$242.5211	$242.52	$242.50	$242.50
Purchase #4	$233.81	4.678%	$244.7476	$244.75	$244.75	$244.70
Purchase #5	$188.50	13.515%	$213.9758	$213.98	$214.00	$214.00
Purchase #6	$212.64	4.865%	$222.9849	$222.98	$223.00	$223.00
Purchase #7	$118.55	7.554%	$127.5053	$127.51	$127.50	$127.50
7 purchase totals =	$1,101.72		$1,195.9749	$1,195.98	$1,195.95	$1,195.90