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	$74.61	4.852%	$78.2301	$78.23	$78.25	$78.20
Purchase #2	$9.60	11.301%	$10.6849	$10.68	$10.70	$10.70
Purchase #3	$189.55	11.515%	$211.3767	$211.38	$211.40	$211.40
Purchase #4	$240.27	4.252%	$250.4863	$250.49	$250.50	$250.50
Purchase #5	$17.30	13.401%	$19.6184	$19.62	$19.60	$19.60
Purchase #6	$178.91	4.756%	$187.419	$187.42	$187.40	$187.40
Purchase #7	$134.88	3.308%	$139.3418	$139.34	$139.35	$139.30
7 purchase totals =	$845.12		$897.1572	$897.16	$897.20	$897.10