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	$156.73	11.769%	$175.1756	$175.18	$175.20	$175.20
Purchase #2	$17.79	9.755%	$19.5254	$19.53	$19.55	$19.50
Purchase #3	$127.43	9.374%	$139.3753	$139.38	$139.40	$139.40
Purchase #4	$30.40	6.223%	$32.2918	$32.29	$32.30	$32.30
Purchase #5	$100.54	10.714%	$111.3119	$111.31	$111.30	$111.30
Purchase #6	$62.73	4.173%	$65.3477	$65.35	$65.35	$65.30
Purchase #7	$103.42	4.310%	$107.8774	$107.88	$107.90	$107.90
7 purchase totals =	$599.04		$650.9051	$650.92	$651.00	$650.90