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	$76.64	11.535%	$85.4804	$85.48	$85.50	$85.50
Purchase #2	$127.29	11.153%	$141.4867	$141.49	$141.50	$141.50
Purchase #3	$167.80	11.642%	$187.3353	$187.34	$187.35	$187.30
Purchase #4	$83.64	13.378%	$94.8294	$94.83	$94.85	$94.80
Purchase #5	$199.69	11.258%	$222.1711	$222.17	$222.15	$222.20
Purchase #6	$26.57	8.328%	$28.7827	$28.78	$28.80	$28.80
Purchase #7	$182.67	9.281%	$199.6236	$199.62	$199.60	$199.60
7 purchase totals =	$864.30		$959.7092	$959.71	$959.75	$959.70