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	$120.44	5.812%	$127.44	$127.44	$127.45	$127.40
Purchase #2	$68.88	13.697%	$78.3145	$78.31	$78.30	$78.30
Purchase #3	$89.40	12.698%	$100.752	$100.75	$100.75	$100.80
Purchase #4	$120.29	10.724%	$133.1899	$133.19	$133.20	$133.20
Purchase #5	$91.29	3.387%	$94.382	$94.38	$94.40	$94.40
Purchase #6	$144.71	5.441%	$152.5837	$152.58	$152.60	$152.60
Purchase #7	$72.51	7.731%	$78.1157	$78.12	$78.10	$78.10
7 purchase totals =	$707.52		$764.7778	$764.77	$764.80	$764.80