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	$24.89	4.205%	$25.9366	$25.94	$25.95	$25.90
Purchase #2	$178.46	12.367%	$200.5301	$200.53	$200.55	$200.50
Purchase #3	$71.65	7.468%	$77.0008	$77.00	$77.00	$77.00
Purchase #4	$155.98	4.382%	$162.815	$162.82	$162.80	$162.80
Purchase #5	$32.77	6.385%	$34.8624	$34.86	$34.85	$34.90
Purchase #6	$118.37	9.814%	$129.9868	$129.99	$130.00	$130.00
Purchase #7	$28.56	10.588%	$31.5839	$31.58	$31.60	$31.60
7 purchase totals =	$610.68		$662.7156	$662.72	$662.75	$662.70