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	$38.35	9.337%	$41.9307	$41.93	$41.95	$41.90
Purchase #2	$229.49	11.333%	$255.4981	$255.50	$255.50	$255.50
Purchase #3	$127.27	12.870%	$143.6496	$143.65	$143.65	$143.60
Purchase #4	$46.89	11.346%	$52.2101	$52.21	$52.20	$52.20
Purchase #5	$70.73	7.666%	$76.1522	$76.15	$76.15	$76.20
Purchase #6	$133.87	6.508%	$142.5823	$142.58	$142.60	$142.60
Purchase #7	$90.94	3.299%	$93.9401	$93.94	$93.95	$93.90
7 purchase totals =	$737.54		$805.9631	$805.96	$806.00	$805.90