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	$127.86	6.461%	$136.121	$136.12	$136.10	$136.10
Purchase #2	$40.68	6.503%	$43.3254	$43.33	$43.35	$43.30
Purchase #3	$173.90	5.159%	$182.8715	$182.87	$182.85	$182.90
Purchase #4	$233.94	12.446%	$263.0562	$263.06	$263.05	$263.10
Purchase #5	$87.78	9.140%	$95.8031	$95.80	$95.80	$95.80
Purchase #6	$127.77	12.239%	$143.4078	$143.41	$143.40	$143.40
Purchase #7	$158.85	5.381%	$167.3977	$167.40	$167.40	$167.40
7 purchase totals =	$950.78		$1,031.9827	$1,031.99	$1,031.95	$1,032.00