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	$49.71	3.312%	$51.3564	$51.36	$51.35	$51.40
Purchase #2	$107.63	3.519%	$111.4175	$111.42	$111.40	$111.40
Purchase #3	$135.36	11.343%	$150.7139	$150.71	$150.70	$150.70
Purchase #4	$13.44	10.837%	$14.8965	$14.90	$14.90	$14.90
Purchase #5	$127.83	10.764%	$141.5896	$141.59	$141.60	$141.60
Purchase #6	$59.69	6.773%	$63.7328	$63.73	$63.75	$63.70
Purchase #7	$111.53	7.404%	$119.7877	$119.79	$119.80	$119.80
7 purchase totals =	$605.19		$653.4944	$653.50	$653.50	$653.50