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	$169.58	6.307%	$180.2754	$180.28	$180.30	$180.30
Purchase #2	$208.31	12.680%	$234.7237	$234.72	$234.70	$234.70
Purchase #3	$36.78	4.432%	$38.4101	$38.41	$38.40	$38.40
Purchase #4	$233.69	9.297%	$255.4162	$255.42	$255.40	$255.40
Purchase #5	$192.91	9.840%	$211.8923	$211.89	$211.90	$211.90
Purchase #6	$45.47	6.592%	$48.4674	$48.47	$48.45	$48.50
Purchase #7	$200.27	8.119%	$216.5299	$216.53	$216.55	$216.50
7 purchase totals =	$1,087.01		$1,185.7150	$1,185.72	$1,185.70	$1,185.70