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	$94.55	13.696%	$107.4996	$107.50	$107.50	$107.50
Purchase #2	$18.88	11.643%	$21.0782	$21.08	$21.10	$21.10
Purchase #3	$39.30	7.244%	$42.1469	$42.15	$42.15	$42.10
Purchase #4	$206.56	10.545%	$228.3418	$228.34	$228.35	$228.30
Purchase #5	$124.87	6.707%	$133.245	$133.25	$133.25	$133.20
Purchase #6	$240.83	9.813%	$264.4626	$264.46	$264.45	$264.50
Purchase #7	$139.83	11.368%	$155.7259	$155.73	$155.75	$155.70
7 purchase totals =	$864.82		$952.5000	$952.51	$952.55	$952.40