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	$147.39	11.686%	$164.614	$164.61	$164.60	$164.60
Purchase #2	$123.58	3.234%	$127.5766	$127.58	$127.60	$127.60
Purchase #3	$215.31	12.731%	$242.7211	$242.72	$242.70	$242.70
Purchase #4	$77.26	5.624%	$81.6051	$81.61	$81.60	$81.60
Purchase #5	$206.52	13.470%	$234.3382	$234.34	$234.35	$234.30
Purchase #6	$26.67	10.394%	$29.4421	$29.44	$29.45	$29.40
Purchase #7	$97.60	5.426%	$102.8958	$102.90	$102.90	$102.90
7 purchase totals =	$894.33		$983.1929	$983.20	$983.20	$983.10