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	$145.62	11.702%	$162.6605	$162.66	$162.65	$162.70
Purchase #2	$95.57	8.382%	$103.5807	$103.58	$103.60	$103.60
Purchase #3	$36.27	12.192%	$40.692	$40.69	$40.70	$40.70
Purchase #4	$19.81	6.566%	$21.1107	$21.11	$21.10	$21.10
Purchase #5	$47.40	12.725%	$53.4317	$53.43	$53.45	$53.40
Purchase #6	$40.25	4.591%	$42.0979	$42.10	$42.10	$42.10
Purchase #7	$33.39	8.754%	$36.313	$36.31	$36.30	$36.30
7 purchase totals =	$418.31		$459.8865	$459.88	$459.90	$459.90