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	$90.57	8.871%	$98.6045	$98.60	$98.60	$98.60
Purchase #2	$9.59	11.505%	$10.6933	$10.69	$10.70	$10.70
Purchase #3	$89.35	10.297%	$98.5504	$98.55	$98.55	$98.60
Purchase #4	$146.73	8.188%	$158.7443	$158.74	$158.75	$158.70
Purchase #5	$179.61	11.741%	$200.698	$200.70	$200.70	$200.70
Purchase #6	$247.93	10.404%	$273.7246	$273.72	$273.70	$273.70
Purchase #7	$89.45	10.592%	$98.9245	$98.92	$98.90	$98.90
7 purchase totals =	$853.23		$939.9396	$939.92	$939.90	$939.90