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	$210.70	5.290%	$221.846	$221.85	$221.85	$221.80
Purchase #2	$245.69	13.322%	$278.4208	$278.42	$278.40	$278.40
Purchase #3	$138.50	3.185%	$142.9112	$142.91	$142.90	$142.90
Purchase #4	$84.42	4.431%	$88.1607	$88.16	$88.15	$88.20
Purchase #5	$48.90	11.275%	$54.4135	$54.41	$54.40	$54.40
Purchase #6	$12.76	12.193%	$14.3158	$14.32	$14.30	$14.30
Purchase #7	$218.83	4.326%	$228.2966	$228.30	$228.30	$228.30
7 purchase totals =	$959.80		$1,028.3646	$1,028.37	$1,028.30	$1,028.30