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	$232.73	9.612%	$255.1	$255.10	$255.10	$255.10
Purchase #2	$220.58	13.462%	$250.2745	$250.27	$250.25	$250.30
Purchase #3	$207.51	13.199%	$234.8992	$234.90	$234.90	$234.90
Purchase #4	$48.82	9.407%	$53.4125	$53.41	$53.40	$53.40
Purchase #5	$203.94	7.551%	$219.3395	$219.34	$219.35	$219.30
Purchase #6	$223.28	6.769%	$238.3938	$238.39	$238.40	$238.40
Purchase #7	$31.99	3.647%	$33.1567	$33.16	$33.15	$33.20
7 purchase totals =	$1,168.85		$1,284.5762	$1,284.57	$1,284.55	$1,284.60