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	$174.26	12.628%	$196.2656	$196.27	$196.25	$196.30
Purchase #2	$24.30	9.856%	$26.695	$26.70	$26.70	$26.70
Purchase #3	$54.29	9.453%	$59.422	$59.42	$59.40	$59.40
Purchase #4	$189.80	3.466%	$196.3785	$196.38	$196.40	$196.40
Purchase #5	$94.25	6.446%	$100.3254	$100.33	$100.35	$100.30
Purchase #6	$30.82	13.243%	$34.9015	$34.90	$34.90	$34.90
Purchase #7	$28.70	7.622%	$30.8875	$30.89	$30.90	$30.90
7 purchase totals =	$596.42		$644.8755	$644.89	$644.90	$644.90