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	$49.53	8.780%	$53.8787	$53.88	$53.90	$53.90
Purchase #2	$37.65	4.732%	$39.4316	$39.43	$39.45	$39.40
Purchase #3	$225.38	10.663%	$249.4123	$249.41	$249.40	$249.40
Purchase #4	$195.34	9.788%	$214.4599	$214.46	$214.45	$214.50
Purchase #5	$40.94	4.199%	$42.6591	$42.66	$42.65	$42.70
Purchase #6	$188.39	13.839%	$214.4613	$214.46	$214.45	$214.50
Purchase #7	$217.60	13.235%	$246.3994	$246.40	$246.40	$246.40
7 purchase totals =	$954.83		$1,060.7023	$1,060.70	$1,060.70	$1,060.80