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	$131.42	7.182%	$140.8586	$140.86	$140.85	$140.90
Purchase #2	$118.80	13.293%	$134.5921	$134.59	$134.60	$134.60
Purchase #3	$173.64	4.618%	$181.6587	$181.66	$181.65	$181.70
Purchase #4	$151.90	13.452%	$172.3336	$172.33	$172.35	$172.30
Purchase #5	$173.96	12.145%	$195.0874	$195.09	$195.10	$195.10
Purchase #6	$187.87	4.512%	$196.3467	$196.35	$196.35	$196.30
Purchase #7	$153.77	4.517%	$160.7158	$160.72	$160.70	$160.70
7 purchase totals =	$1,091.36		$1,181.5929	$1,181.60	$1,181.60	$1,181.60