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	$225.39	7.133%	$241.4671	$241.47	$241.45	$241.50
Purchase #2	$162.90	6.661%	$173.7508	$173.75	$173.75	$173.80
Purchase #3	$159.83	13.436%	$181.3048	$181.30	$181.30	$181.30
Purchase #4	$42.71	11.442%	$47.5969	$47.60	$47.60	$47.60
Purchase #5	$162.89	4.730%	$170.5947	$170.59	$170.60	$170.60
Purchase #6	$123.81	5.222%	$130.2754	$130.28	$130.30	$130.30
Purchase #7	$110.27	3.526%	$114.1581	$114.16	$114.15	$114.20
7 purchase totals =	$987.80		$1,059.1478	$1,059.15	$1,059.15	$1,059.30