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	$42.58	4.746%	$44.6008	$44.60	$44.60	$44.60
Purchase #2	$147.76	7.384%	$158.6706	$158.67	$158.65	$158.70
Purchase #3	$19.60	12.705%	$22.0902	$22.09	$22.10	$22.10
Purchase #4	$201.31	10.699%	$222.8482	$222.85	$222.85	$222.80
Purchase #5	$225.42	7.498%	$242.322	$242.32	$242.30	$242.30
Purchase #6	$110.33	12.117%	$123.6987	$123.70	$123.70	$123.70
Purchase #7	$99.44	11.785%	$111.159	$111.16	$111.15	$111.20
7 purchase totals =	$846.44		$925.3895	$925.39	$925.35	$925.40