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	$221.54	9.222%	$241.9704	$241.97	$241.95	$242.00
Purchase #2	$46.69	13.284%	$52.8923	$52.89	$52.90	$52.90
Purchase #3	$225.89	8.363%	$244.7812	$244.78	$244.80	$244.80
Purchase #4	$121.91	11.697%	$136.1698	$136.17	$136.15	$136.20
Purchase #5	$223.68	4.431%	$233.5913	$233.59	$233.60	$233.60
Purchase #6	$242.46	13.428%	$275.0175	$275.02	$275.00	$275.00
Purchase #7	$76.27	7.399%	$81.9132	$81.91	$81.90	$81.90
7 purchase totals =	$1,158.44		$1,266.3357	$1,266.33	$1,266.30	$1,266.40