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	$45.89	12.617%	$51.6799	$51.68	$51.70	$51.70
Purchase #2	$102.72	6.244%	$109.1338	$109.13	$109.15	$109.10
Purchase #3	$67.51	3.725%	$70.0247	$70.02	$70.00	$70.00
Purchase #4	$156.73	10.232%	$172.7666	$172.77	$172.75	$172.80
Purchase #5	$211.81	6.868%	$226.3571	$226.36	$226.35	$226.40
Purchase #6	$214.78	3.309%	$221.8871	$221.89	$221.90	$221.90
Purchase #7	$65.28	12.841%	$73.6626	$73.66	$73.65	$73.70
7 purchase totals =	$864.72		$925.5118	$925.51	$925.50	$925.60