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	$69.82	12.367%	$78.4546	$78.45	$78.45	$78.50
Purchase #2	$114.29	13.376%	$129.5774	$129.58	$129.60	$129.60
Purchase #3	$106.57	4.494%	$111.3593	$111.36	$111.35	$111.40
Purchase #4	$185.48	4.840%	$194.4572	$194.46	$194.45	$194.50
Purchase #5	$140.31	8.238%	$151.8687	$151.87	$151.85	$151.90
Purchase #6	$23.88	4.485%	$24.951	$24.95	$24.95	$25.00
Purchase #7	$36.49	13.169%	$41.2954	$41.30	$41.30	$41.30
7 purchase totals =	$676.84		$731.9636	$731.97	$731.95	$732.20