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	$180.27	11.445%	$200.9019	$200.90	$200.90	$200.90
Purchase #2	$26.50	7.508%	$28.4896	$28.49	$28.50	$28.50
Purchase #3	$52.86	12.575%	$59.5071	$59.51	$59.50	$59.50
Purchase #4	$38.87	7.622%	$41.8327	$41.83	$41.85	$41.80
Purchase #5	$16.71	5.836%	$17.6852	$17.69	$17.70	$17.70
Purchase #6	$37.49	11.121%	$41.6593	$41.66	$41.65	$41.70
Purchase #7	$13.70	6.382%	$14.5743	$14.57	$14.55	$14.60
7 purchase totals =	$366.40		$404.6501	$404.65	$404.65	$404.70