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	$114.85	7.265%	$123.1939	$123.19	$123.20	$123.20
Purchase #2	$232.86	10.165%	$256.5302	$256.53	$256.55	$256.50
Purchase #3	$177.33	8.165%	$191.809	$191.81	$191.80	$191.80
Purchase #4	$59.89	11.215%	$66.6067	$66.61	$66.60	$66.60
Purchase #5	$170.66	9.764%	$187.3232	$187.32	$187.30	$187.30
Purchase #6	$127.53	9.788%	$140.0126	$140.01	$140.00	$140.00
Purchase #7	$79.50	6.301%	$84.5093	$84.51	$84.50	$84.50
7 purchase totals =	$962.62		$1,049.9849	$1,049.98	$1,049.95	$1,049.90