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	$176.41	12.265%	$198.0467	$198.05	$198.05	$198.00
Purchase #2	$131.84	12.670%	$148.5441	$148.54	$148.55	$148.50
Purchase #3	$199.52	6.725%	$212.9377	$212.94	$212.95	$212.90
Purchase #4	$40.38	13.662%	$45.8967	$45.90	$45.90	$45.90
Purchase #5	$36.31	4.738%	$38.0304	$38.03	$38.05	$38.00
Purchase #6	$146.46	4.676%	$153.3085	$153.31	$153.30	$153.30
Purchase #7	$183.70	13.548%	$208.5877	$208.59	$208.60	$208.60
7 purchase totals =	$914.62		$1,005.3518	$1,005.36	$1,005.40	$1,005.20