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	$216.75	13.444%	$245.8899	$245.89	$245.90	$245.90
Purchase #2	$242.60	13.358%	$275.0065	$275.01	$275.00	$275.00
Purchase #3	$150.54	9.652%	$165.0701	$165.07	$165.05	$165.10
Purchase #4	$222.34	9.153%	$242.6908	$242.69	$242.70	$242.70
Purchase #5	$160.74	4.783%	$168.4282	$168.43	$168.45	$168.40
Purchase #6	$55.31	3.815%	$57.4201	$57.42	$57.40	$57.40
Purchase #7	$136.36	5.361%	$143.6703	$143.67	$143.65	$143.70
7 purchase totals =	$1,184.64		$1,298.1759	$1,298.18	$1,298.15	$1,298.20