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	$85.37	12.632%	$96.1539	$96.15	$96.15	$96.20
Purchase #2	$104.48	7.227%	$112.0308	$112.03	$112.05	$112.00
Purchase #3	$77.94	6.707%	$83.1674	$83.17	$83.15	$83.20
Purchase #4	$34.28	4.173%	$35.7105	$35.71	$35.70	$35.70
Purchase #5	$149.42	10.616%	$165.2824	$165.28	$165.30	$165.30
Purchase #6	$141.32	3.353%	$146.0585	$146.06	$146.05	$146.10
Purchase #7	$201.58	10.353%	$222.4496	$222.45	$222.45	$222.40
7 purchase totals =	$794.39		$860.8531	$860.85	$860.85	$860.90