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	$187.81	4.589%	$196.4286	$196.43	$196.45	$196.40
Purchase #2	$130.31	3.502%	$134.8735	$134.87	$134.85	$134.90
Purchase #3	$51.52	12.444%	$57.9311	$57.93	$57.95	$57.90
Purchase #4	$126.74	12.166%	$142.1592	$142.16	$142.15	$142.20
Purchase #5	$243.40	7.842%	$262.4874	$262.49	$262.50	$262.50
Purchase #6	$177.42	13.247%	$200.9228	$200.92	$200.90	$200.90
Purchase #7	$128.96	6.729%	$137.6377	$137.64	$137.65	$137.60
7 purchase totals =	$1,046.16		$1,132.4403	$1,132.44	$1,132.45	$1,132.40