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	$67.96	6.679%	$72.499	$72.50	$72.50	$72.50
Purchase #2	$199.81	7.534%	$214.8637	$214.86	$214.85	$214.90
Purchase #3	$175.92	8.283%	$190.4915	$190.49	$190.50	$190.50
Purchase #4	$66.67	11.288%	$74.1957	$74.20	$74.20	$74.20
Purchase #5	$191.74	10.200%	$211.2975	$211.30	$211.30	$211.30
Purchase #6	$239.96	9.334%	$262.3579	$262.36	$262.35	$262.40
Purchase #7	$74.91	11.411%	$83.458	$83.46	$83.45	$83.50
7 purchase totals =	$1,016.97		$1,109.1633	$1,109.17	$1,109.15	$1,109.30