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	$184.50	3.627%	$191.1918	$191.19	$191.20	$191.20
Purchase #2	$70.68	11.105%	$78.529	$78.53	$78.55	$78.50
Purchase #3	$129.84	13.204%	$146.9841	$146.98	$147.00	$147.00
Purchase #4	$137.76	9.772%	$151.2219	$151.22	$151.20	$151.20
Purchase #5	$56.53	4.625%	$59.1445	$59.14	$59.15	$59.10
Purchase #6	$29.37	11.381%	$32.7126	$32.71	$32.70	$32.70
Purchase #7	$191.53	4.679%	$200.4917	$200.49	$200.50	$200.50
7 purchase totals =	$800.21		$860.2756	$860.26	$860.30	$860.20