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	$40.38	6.654%	$43.0669	$43.07	$43.05	$43.10
Purchase #2	$94.57	5.389%	$99.6664	$99.67	$99.65	$99.70
Purchase #3	$63.84	8.436%	$69.2255	$69.23	$69.25	$69.20
Purchase #4	$215.87	10.440%	$238.4068	$238.41	$238.40	$238.40
Purchase #5	$219.36	10.653%	$242.7284	$242.73	$242.75	$242.70
Purchase #6	$192.90	9.181%	$210.6101	$210.61	$210.60	$210.60
Purchase #7	$100.66	13.125%	$113.8716	$113.87	$113.85	$113.90
7 purchase totals =	$927.58		$1,017.5757	$1,017.59	$1,017.55	$1,017.60