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	$60.92	9.103%	$66.4655	$66.47	$66.45	$66.50
Purchase #2	$247.72	8.112%	$267.815	$267.82	$267.80	$267.80
Purchase #3	$173.82	13.252%	$196.8546	$196.85	$196.85	$196.90
Purchase #4	$37.93	7.370%	$40.7254	$40.73	$40.75	$40.70
Purchase #5	$198.59	8.607%	$215.6826	$215.68	$215.70	$215.70
Purchase #6	$178.41	9.259%	$194.929	$194.93	$194.95	$194.90
Purchase #7	$166.81	13.338%	$189.0591	$189.06	$189.05	$189.10
7 purchase totals =	$1,064.20		$1,171.5312	$1,171.54	$1,171.55	$1,171.60