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	$36.39	11.108%	$40.4322	$40.43	$40.45	$40.40
Purchase #2	$224.55	5.331%	$236.5208	$236.52	$236.50	$236.50
Purchase #3	$52.57	3.368%	$54.3406	$54.34	$54.35	$54.30
Purchase #4	$68.48	8.687%	$74.4289	$74.43	$74.45	$74.40
Purchase #5	$248.83	13.696%	$282.9098	$282.91	$282.90	$282.90
Purchase #6	$152.94	3.687%	$158.5789	$158.58	$158.60	$158.60
Purchase #7	$147.69	5.155%	$155.3034	$155.30	$155.30	$155.30
7 purchase totals =	$931.45		$1,002.5146	$1,002.51	$1,002.55	$1,002.40