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	$88.89	11.125%	$98.779	$98.78	$98.80	$98.80
Purchase #2	$81.43	11.405%	$90.7171	$90.72	$90.70	$90.70
Purchase #3	$37.36	9.467%	$40.8969	$40.90	$40.90	$40.90
Purchase #4	$33.60	3.816%	$34.8822	$34.88	$34.90	$34.90
Purchase #5	$230.70	9.826%	$253.3686	$253.37	$253.35	$253.40
Purchase #6	$240.74	6.655%	$256.7612	$256.76	$256.75	$256.80
Purchase #7	$60.39	13.617%	$68.6133	$68.61	$68.60	$68.60
7 purchase totals =	$773.11		$844.0183	$844.02	$844.00	$844.10