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	$195.35	6.123%	$207.3113	$207.31	$207.30	$207.30
Purchase #2	$219.38	4.141%	$228.4645	$228.46	$228.45	$228.50
Purchase #3	$11.55	12.857%	$13.035	$13.04	$13.05	$13.00
Purchase #4	$227.48	10.124%	$250.5101	$250.51	$250.50	$250.50
Purchase #5	$150.62	10.279%	$166.1022	$166.10	$166.10	$166.10
Purchase #6	$111.37	6.500%	$118.6091	$118.61	$118.60	$118.60
Purchase #7	$100.32	10.110%	$110.4624	$110.46	$110.45	$110.50
7 purchase totals =	$1,016.07		$1,094.4946	$1,094.49	$1,094.45	$1,094.50