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	$204.55	4.863%	$214.4973	$214.50	$214.50	$214.50
Purchase #2	$88.90	13.636%	$101.0224	$101.02	$101.00	$101.00
Purchase #3	$40.84	4.272%	$42.5847	$42.58	$42.60	$42.60
Purchase #4	$210.90	7.311%	$226.3189	$226.32	$226.30	$226.30
Purchase #5	$182.41	4.191%	$190.0548	$190.05	$190.05	$190.10
Purchase #6	$99.41	10.451%	$109.7993	$109.80	$109.80	$109.80
Purchase #7	$58.73	4.748%	$61.5185	$61.52	$61.50	$61.50
7 purchase totals =	$885.74		$945.7959	$945.79	$945.75	$945.80