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	$170.72	4.434%	$178.2897	$178.29	$178.30	$178.30
Purchase #2	$15.91	10.475%	$17.5766	$17.58	$17.60	$17.60
Purchase #3	$118.46	11.486%	$132.0663	$132.07	$132.05	$132.10
Purchase #4	$123.85	9.529%	$135.6517	$135.65	$135.65	$135.70
Purchase #5	$162.92	5.107%	$171.2403	$171.24	$171.25	$171.20
Purchase #6	$151.83	10.320%	$167.4989	$167.50	$167.50	$167.50
Purchase #7	$245.81	7.628%	$264.5604	$264.56	$264.55	$264.60
7 purchase totals =	$989.50		$1,066.8839	$1,066.89	$1,066.90	$1,067.00