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	$123.67	5.498%	$130.4694	$130.47	$130.45	$130.50
Purchase #2	$167.77	12.856%	$189.3385	$189.34	$189.35	$189.30
Purchase #3	$184.42	4.501%	$192.7207	$192.72	$192.70	$192.70
Purchase #4	$112.92	12.792%	$127.3647	$127.36	$127.35	$127.40
Purchase #5	$72.89	13.811%	$82.9568	$82.96	$82.95	$83.00
Purchase #6	$209.97	8.326%	$227.4521	$227.45	$227.45	$227.50
Purchase #7	$173.77	11.874%	$194.4034	$194.40	$194.40	$194.40
7 purchase totals =	$1,045.41		$1,144.7056	$1,144.70	$1,144.65	$1,144.80