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	$173.28	9.409%	$189.5839	$189.58	$189.60	$189.60
Purchase #2	$118.69	11.563%	$132.4141	$132.41	$132.40	$132.40
Purchase #3	$27.30	8.485%	$29.6164	$29.62	$29.60	$29.60
Purchase #4	$185.48	5.741%	$196.1284	$196.13	$196.15	$196.10
Purchase #5	$55.48	7.667%	$59.7337	$59.73	$59.75	$59.70
Purchase #6	$172.31	4.108%	$179.3885	$179.39	$179.40	$179.40
Purchase #7	$188.39	11.471%	$210.0002	$210.00	$210.00	$210.00
7 purchase totals =	$920.93		$996.8652	$996.86	$996.90	$996.80