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	$127.66	5.654%	$134.8779	$134.88	$134.90	$134.90
Purchase #2	$19.45	4.152%	$20.2576	$20.26	$20.25	$20.30
Purchase #3	$55.78	5.845%	$59.0403	$59.04	$59.05	$59.00
Purchase #4	$72.37	5.130%	$76.0826	$76.08	$76.10	$76.10
Purchase #5	$154.70	13.485%	$175.5613	$175.56	$175.55	$175.60
Purchase #6	$163.75	6.791%	$174.8703	$174.87	$174.85	$174.90
Purchase #7	$197.54	11.721%	$220.6937	$220.69	$220.70	$220.70
7 purchase totals =	$791.25		$861.3837	$861.38	$861.40	$861.50