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	$145.40	8.242%	$157.3839	$157.38	$157.40	$157.40
Purchase #2	$92.49	7.618%	$99.5359	$99.54	$99.55	$99.50
Purchase #3	$118.48	13.499%	$134.4736	$134.47	$134.45	$134.50
Purchase #4	$46.70	4.334%	$48.724	$48.72	$48.70	$48.70
Purchase #5	$148.33	3.318%	$153.2516	$153.25	$153.25	$153.30
Purchase #6	$243.93	7.496%	$262.215	$262.22	$262.20	$262.20
Purchase #7	$80.41	7.852%	$86.7238	$86.72	$86.70	$86.70
7 purchase totals =	$875.74		$942.3078	$942.30	$942.25	$942.30