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	$20.40	11.545%	$22.7552	$22.76	$22.75	$22.80
Purchase #2	$90.48	8.342%	$98.0278	$98.03	$98.05	$98.00
Purchase #3	$122.46	7.684%	$131.8698	$131.87	$131.85	$131.90
Purchase #4	$104.62	8.746%	$113.7701	$113.77	$113.75	$113.80
Purchase #5	$159.94	9.870%	$175.7261	$175.73	$175.75	$175.70
Purchase #6	$47.91	13.261%	$54.2633	$54.26	$54.25	$54.30
Purchase #7	$106.69	4.801%	$111.8122	$111.81	$111.80	$111.80
7 purchase totals =	$652.50		$708.2245	$708.23	$708.20	$708.30