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	$95.83	4.174%	$99.8299	$99.83	$99.85	$99.80
Purchase #2	$14.37	4.673%	$15.0415	$15.04	$15.05	$15.00
Purchase #3	$135.95	12.558%	$153.0226	$153.02	$153.00	$153.00
Purchase #4	$93.92	10.604%	$103.8793	$103.88	$103.90	$103.90
Purchase #5	$137.57	3.647%	$142.5872	$142.59	$142.60	$142.60
Purchase #6	$150.80	8.787%	$164.0508	$164.05	$164.05	$164.10
Purchase #7	$19.62	13.554%	$22.2793	$22.28	$22.30	$22.30
7 purchase totals =	$648.06		$700.6906	$700.69	$700.75	$700.70