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	$211.74	10.465%	$233.8986	$233.90	$233.90	$233.90
Purchase #2	$38.97	11.831%	$43.5805	$43.58	$43.60	$43.60
Purchase #3	$238.41	8.476%	$258.6176	$258.62	$258.60	$258.60
Purchase #4	$83.37	5.386%	$87.8603	$87.86	$87.85	$87.90
Purchase #5	$10.50	8.235%	$11.3647	$11.36	$11.35	$11.40
Purchase #6	$111.31	3.132%	$114.7962	$114.80	$114.80	$114.80
Purchase #7	$37.77	13.142%	$42.7337	$42.73	$42.75	$42.70
7 purchase totals =	$732.07		$792.8516	$792.85	$792.85	$792.90