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	$246.25	4.152%	$256.4743	$256.47	$256.45	$256.50
Purchase #2	$131.99	13.140%	$149.3335	$149.33	$149.35	$149.30
Purchase #3	$59.81	4.339%	$62.4052	$62.41	$62.40	$62.40
Purchase #4	$149.31	12.176%	$167.49	$167.49	$167.50	$167.50
Purchase #5	$141.43	11.238%	$157.3239	$157.32	$157.30	$157.30
Purchase #6	$123.28	3.714%	$127.8586	$127.86	$127.85	$127.90
Purchase #7	$208.88	8.409%	$226.4447	$226.44	$226.45	$226.40
7 purchase totals =	$1,060.95		$1,147.3302	$1,147.32	$1,147.30	$1,147.30