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	$40.95	7.780%	$44.1359	$44.14	$44.15	$44.10
Purchase #2	$36.37	3.165%	$37.5211	$37.52	$37.50	$37.50
Purchase #3	$157.31	9.268%	$171.8895	$171.89	$171.90	$171.90
Purchase #4	$219.57	10.491%	$242.6051	$242.61	$242.60	$242.60
Purchase #5	$44.37	5.584%	$46.8476	$46.85	$46.85	$46.80
Purchase #6	$167.34	9.430%	$183.1202	$183.12	$183.10	$183.10
Purchase #7	$112.39	13.568%	$127.6391	$127.64	$127.65	$127.60
7 purchase totals =	$778.30		$853.7585	$853.77	$853.75	$853.60