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	$172.67	5.420%	$182.0287	$182.03	$182.05	$182.00
Purchase #2	$120.89	10.821%	$133.9715	$133.97	$133.95	$134.00
Purchase #3	$208.90	3.549%	$216.3139	$216.31	$216.30	$216.30
Purchase #4	$135.71	11.585%	$151.432	$151.43	$151.45	$151.40
Purchase #5	$107.35	3.776%	$111.4035	$111.40	$111.40	$111.40
Purchase #6	$228.86	6.307%	$243.2942	$243.29	$243.30	$243.30
Purchase #7	$28.44	4.676%	$29.7699	$29.77	$29.75	$29.80
7 purchase totals =	$1,002.82		$1,068.2137	$1,068.20	$1,068.20	$1,068.20