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	$139.51	3.461%	$144.3384	$144.34	$144.35	$144.30
Purchase #2	$90.34	10.567%	$99.8862	$99.89	$99.90	$99.90
Purchase #3	$156.41	11.695%	$174.7021	$174.70	$174.70	$174.70
Purchase #4	$67.48	4.407%	$70.4538	$70.45	$70.45	$70.50
Purchase #5	$12.91	9.249%	$14.104	$14.10	$14.10	$14.10
Purchase #6	$55.38	5.807%	$58.5959	$58.60	$58.60	$58.60
Purchase #7	$211.53	7.113%	$226.5761	$226.58	$226.60	$226.60
7 purchase totals =	$733.56		$788.6565	$788.66	$788.70	$788.70