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	$230.91	7.736%	$248.7732	$248.77	$248.75	$248.80
Purchase #2	$54.35	3.139%	$56.056	$56.06	$56.05	$56.10
Purchase #3	$58.36	11.546%	$65.0982	$65.10	$65.10	$65.10
Purchase #4	$24.58	3.360%	$25.4059	$25.41	$25.40	$25.40
Purchase #5	$234.27	13.806%	$266.6133	$266.61	$266.60	$266.60
Purchase #6	$142.32	7.132%	$152.4703	$152.47	$152.45	$152.50
Purchase #7	$173.50	8.411%	$188.0931	$188.09	$188.10	$188.10
7 purchase totals =	$918.29		$1,002.5100	$1,002.51	$1,002.45	$1,002.60