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	$43.55	7.313%	$46.7348	$46.73	$46.75	$46.70
Purchase #2	$132.79	11.545%	$148.1206	$148.12	$148.10	$148.10
Purchase #3	$76.38	3.143%	$78.7806	$78.78	$78.80	$78.80
Purchase #4	$158.64	5.284%	$167.0225	$167.02	$167.00	$167.00
Purchase #5	$66.64	9.733%	$73.1261	$73.13	$73.15	$73.10
Purchase #6	$168.30	12.226%	$188.8764	$188.88	$188.90	$188.90
Purchase #7	$152.92	10.756%	$169.3681	$169.37	$169.35	$169.40
7 purchase totals =	$799.22		$872.0291	$872.03	$872.05	$872.00