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	$204.32	8.738%	$222.1735	$222.17	$222.15	$222.20
Purchase #2	$74.59	4.733%	$78.1203	$78.12	$78.10	$78.10
Purchase #3	$246.45	5.556%	$260.1428	$260.14	$260.15	$260.10
Purchase #4	$214.68	9.146%	$234.3146	$234.31	$234.30	$234.30
Purchase #5	$94.90	12.679%	$106.9324	$106.93	$106.95	$106.90
Purchase #6	$166.98	6.645%	$178.0758	$178.08	$178.10	$178.10
Purchase #7	$67.48	6.396%	$71.796	$71.80	$71.80	$71.80
7 purchase totals =	$1,069.40		$1,151.5554	$1,151.55	$1,151.55	$1,151.50