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	$205.42	7.583%	$220.997	$221.00	$221.00	$221.00
Purchase #2	$59.71	6.345%	$63.4986	$63.50	$63.50	$63.50
Purchase #3	$152.92	8.480%	$165.8876	$165.89	$165.90	$165.90
Purchase #4	$38.25	11.612%	$42.6916	$42.69	$42.70	$42.70
Purchase #5	$168.65	8.187%	$182.4574	$182.46	$182.45	$182.50
Purchase #6	$157.25	5.240%	$165.4899	$165.49	$165.50	$165.50
Purchase #7	$148.58	6.400%	$158.0891	$158.09	$158.10	$158.10
7 purchase totals =	$930.78		$999.1112	$999.12	$999.15	$999.20