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	$173.60	7.440%	$186.5158	$186.52	$186.50	$186.50
Purchase #2	$242.93	5.159%	$255.4628	$255.46	$255.45	$255.50
Purchase #3	$150.33	12.474%	$169.0822	$169.08	$169.10	$169.10
Purchase #4	$196.94	12.840%	$222.2271	$222.23	$222.25	$222.20
Purchase #5	$220.60	5.690%	$233.1521	$233.15	$233.15	$233.20
Purchase #6	$214.70	12.806%	$242.1945	$242.19	$242.20	$242.20
Purchase #7	$24.59	4.692%	$25.7438	$25.74	$25.75	$25.70
7 purchase totals =	$1,223.69		$1,334.3783	$1,334.37	$1,334.40	$1,334.40