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	$48.67	6.821%	$51.9898	$51.99	$52.00	$52.00
Purchase #2	$233.57	9.398%	$255.5209	$255.52	$255.50	$255.50
Purchase #3	$69.84	3.794%	$72.4897	$72.49	$72.50	$72.50
Purchase #4	$241.91	13.845%	$275.4024	$275.40	$275.40	$275.40
Purchase #5	$175.78	7.322%	$188.6506	$188.65	$188.65	$188.70
Purchase #6	$140.28	4.823%	$147.0457	$147.05	$147.05	$147.00
Purchase #7	$83.94	7.556%	$90.2825	$90.28	$90.30	$90.30
7 purchase totals =	$993.99		$1,081.3816	$1,081.38	$1,081.40	$1,081.40