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	$250.78	8.410%	$271.8706	$271.87	$271.85	$271.90
Purchase #2	$177.66	10.823%	$196.8881	$196.89	$196.90	$196.90
Purchase #3	$144.96	7.778%	$156.235	$156.24	$156.25	$156.20
Purchase #4	$52.52	5.568%	$55.4443	$55.44	$55.45	$55.40
Purchase #5	$135.97	10.586%	$150.3638	$150.36	$150.35	$150.40
Purchase #6	$140.88	12.847%	$158.9789	$158.98	$159.00	$159.00
Purchase #7	$9.78	12.440%	$10.9966	$11.00	$11.00	$11.00
7 purchase totals =	$912.55		$1,000.7773	$1,000.78	$1,000.80	$1,000.80