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	$99.77	11.532%	$111.2755	$111.28	$111.30	$111.30
Purchase #2	$50.80	7.563%	$54.642	$54.64	$54.65	$54.60
Purchase #3	$84.82	4.170%	$88.357	$88.36	$88.35	$88.40
Purchase #4	$180.79	5.298%	$190.3683	$190.37	$190.35	$190.40
Purchase #5	$214.89	3.459%	$222.323	$222.32	$222.30	$222.30
Purchase #6	$217.81	7.650%	$234.4725	$234.47	$234.45	$234.50
Purchase #7	$72.26	12.644%	$81.3966	$81.40	$81.40	$81.40
7 purchase totals =	$921.14		$982.8349	$982.84	$982.80	$982.90