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	$235.60	4.477%	$246.1478	$246.15	$246.15	$246.10
Purchase #2	$161.60	13.863%	$184.0026	$184.00	$184.00	$184.00
Purchase #3	$172.99	5.144%	$181.8886	$181.89	$181.90	$181.90
Purchase #4	$129.96	11.159%	$144.4622	$144.46	$144.45	$144.50
Purchase #5	$181.53	7.508%	$195.1593	$195.16	$195.15	$195.20
Purchase #6	$6.31	10.445%	$6.9691	$6.97	$6.95	$7.00
Purchase #7	$85.77	4.806%	$89.8921	$89.89	$89.90	$89.90
7 purchase totals =	$973.76		$1,048.5217	$1,048.52	$1,048.50	$1,048.60