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	$100.90	10.116%	$111.107	$111.11	$111.10	$111.10
Purchase #2	$139.74	7.423%	$150.1129	$150.11	$150.10	$150.10
Purchase #3	$48.35	7.453%	$51.9535	$51.95	$51.95	$52.00
Purchase #4	$139.42	8.391%	$151.1187	$151.12	$151.10	$151.10
Purchase #5	$52.35	12.164%	$58.7179	$58.72	$58.70	$58.70
Purchase #6	$233.66	7.481%	$251.1401	$251.14	$251.15	$251.10
Purchase #7	$118.70	7.331%	$127.4019	$127.40	$127.40	$127.40
7 purchase totals =	$833.12		$901.5520	$901.55	$901.50	$901.50