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	$133.64	7.510%	$143.6764	$143.68	$143.70	$143.70
Purchase #2	$164.71	10.428%	$181.886	$181.89	$181.90	$181.90
Purchase #3	$95.76	5.102%	$100.6457	$100.65	$100.65	$100.60
Purchase #4	$208.87	8.625%	$226.885	$226.89	$226.90	$226.90
Purchase #5	$44.69	12.199%	$50.1417	$50.14	$50.15	$50.10
Purchase #6	$100.87	7.375%	$108.3092	$108.31	$108.30	$108.30
Purchase #7	$59.98	4.546%	$62.7067	$62.71	$62.70	$62.70
7 purchase totals =	$808.52		$874.2507	$874.27	$874.30	$874.20