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	$51.38	10.724%	$56.89	$56.89	$56.90	$56.90
Purchase #2	$6.46	9.812%	$7.0939	$7.09	$7.10	$7.10
Purchase #3	$174.72	8.423%	$189.4367	$189.44	$189.45	$189.40
Purchase #4	$92.29	13.760%	$104.9891	$104.99	$105.00	$105.00
Purchase #5	$247.88	13.857%	$282.2287	$282.23	$282.25	$282.20
Purchase #6	$147.26	5.749%	$155.726	$155.73	$155.75	$155.70
Purchase #7	$153.87	7.332%	$165.1517	$165.15	$165.15	$165.20
7 purchase totals =	$873.86		$961.5161	$961.52	$961.60	$961.50