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	$105.66	12.205%	$118.5558	$118.56	$118.55	$118.60
Purchase #2	$10.95	3.498%	$11.333	$11.33	$11.35	$11.30
Purchase #3	$180.85	11.623%	$201.8702	$201.87	$201.85	$201.90
Purchase #4	$40.94	3.857%	$42.5191	$42.52	$42.50	$42.50
Purchase #5	$58.52	4.575%	$61.1973	$61.20	$61.20	$61.20
Purchase #6	$240.32	6.266%	$255.3785	$255.38	$255.40	$255.40
Purchase #7	$55.78	3.232%	$57.5828	$57.58	$57.60	$57.60
7 purchase totals =	$693.02		$748.4367	$748.44	$748.45	$748.50