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	$241.83	12.452%	$271.9427	$271.94	$271.95	$271.90
Purchase #2	$219.87	11.610%	$245.3969	$245.40	$245.40	$245.40
Purchase #3	$82.50	3.205%	$85.1441	$85.14	$85.15	$85.10
Purchase #4	$132.62	13.451%	$150.4587	$150.46	$150.45	$150.50
Purchase #5	$152.58	5.238%	$160.5721	$160.57	$160.55	$160.60
Purchase #6	$100.44	3.209%	$103.6631	$103.66	$103.65	$103.70
Purchase #7	$210.61	12.667%	$237.288	$237.29	$237.30	$237.30
7 purchase totals =	$1,140.45		$1,254.4656	$1,254.46	$1,254.45	$1,254.50