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	$145.61	3.206%	$150.2783	$150.28	$150.30	$150.30
Purchase #2	$70.32	8.749%	$76.4723	$76.47	$76.45	$76.50
Purchase #3	$51.69	8.407%	$56.0356	$56.04	$56.05	$56.00
Purchase #4	$131.28	11.766%	$146.7264	$146.73	$146.75	$146.70
Purchase #5	$122.57	4.448%	$128.0219	$128.02	$128.00	$128.00
Purchase #6	$102.81	6.142%	$109.1246	$109.12	$109.10	$109.10
Purchase #7	$121.38	13.624%	$137.9168	$137.92	$137.90	$137.90
7 purchase totals =	$745.66		$804.5759	$804.58	$804.55	$804.50