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	$247.31	5.389%	$260.6375	$260.64	$260.65	$260.60
Purchase #2	$186.96	3.834%	$194.128	$194.13	$194.15	$194.10
Purchase #3	$112.58	12.458%	$126.6052	$126.61	$126.60	$126.60
Purchase #4	$63.46	13.490%	$72.0208	$72.02	$72.00	$72.00
Purchase #5	$208.91	6.702%	$222.9111	$222.91	$222.90	$222.90
Purchase #6	$153.73	3.165%	$158.5956	$158.60	$158.60	$158.60
Purchase #7	$171.52	10.661%	$189.8057	$189.81	$189.80	$189.80
7 purchase totals =	$1,144.47		$1,224.7039	$1,224.72	$1,224.70	$1,224.60