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	$195.40	11.190%	$217.2653	$217.27	$217.25	$217.30
Purchase #2	$224.41	7.827%	$241.9746	$241.97	$241.95	$242.00
Purchase #3	$186.61	6.460%	$198.665	$198.67	$198.65	$198.70
Purchase #4	$53.27	11.274%	$59.2757	$59.28	$59.30	$59.30
Purchase #5	$11.25	13.163%	$12.7308	$12.73	$12.75	$12.70
Purchase #6	$146.28	6.364%	$155.5893	$155.59	$155.60	$155.60
Purchase #7	$33.81	10.620%	$37.4006	$37.40	$37.40	$37.40
7 purchase totals =	$851.03		$922.9013	$922.91	$922.90	$923.00