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	$10.75	6.614%	$11.461	$11.46	$11.45	$11.50
Purchase #2	$29.80	11.569%	$33.2476	$33.25	$33.25	$33.20
Purchase #3	$248.90	9.741%	$273.1453	$273.15	$273.15	$273.10
Purchase #4	$66.96	8.487%	$72.6429	$72.64	$72.65	$72.60
Purchase #5	$248.26	3.452%	$256.8299	$256.83	$256.85	$256.80
Purchase #6	$131.84	12.513%	$148.3371	$148.34	$148.35	$148.30
Purchase #7	$25.91	4.395%	$27.0487	$27.05	$27.05	$27.00
7 purchase totals =	$762.42		$822.7125	$822.72	$822.75	$822.50