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	$10.87	9.401%	$11.8919	$11.89	$11.90	$11.90
Purchase #2	$209.95	6.434%	$223.4582	$223.46	$223.45	$223.50
Purchase #3	$34.79	6.844%	$37.171	$37.17	$37.15	$37.20
Purchase #4	$77.88	3.125%	$80.3138	$80.31	$80.30	$80.30
Purchase #5	$92.61	11.495%	$103.2555	$103.26	$103.25	$103.30
Purchase #6	$42.34	7.749%	$45.6209	$45.62	$45.60	$45.60
Purchase #7	$211.50	5.857%	$223.8876	$223.89	$223.90	$223.90
7 purchase totals =	$679.94		$725.5989	$725.60	$725.55	$725.70