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	$156.73	12.399%	$176.163	$176.16	$176.15	$176.20
Purchase #2	$31.73	12.236%	$35.6125	$35.61	$35.60	$35.60
Purchase #3	$18.91	13.522%	$21.467	$21.47	$21.45	$21.50
Purchase #4	$204.91	13.174%	$231.9048	$231.90	$231.90	$231.90
Purchase #5	$93.42	7.309%	$100.2481	$100.25	$100.25	$100.20
Purchase #6	$233.39	6.652%	$248.9151	$248.92	$248.90	$248.90
Purchase #7	$127.39	11.262%	$141.7367	$141.74	$141.75	$141.70
7 purchase totals =	$866.48		$956.0472	$956.05	$956.00	$956.00