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	$92.83	5.817%	$98.2299	$98.23	$98.25	$98.20
Purchase #2	$41.47	5.569%	$43.7795	$43.78	$43.80	$43.80
Purchase #3	$125.43	4.567%	$131.1584	$131.16	$131.15	$131.20
Purchase #4	$121.55	10.452%	$134.2544	$134.25	$134.25	$134.30
Purchase #5	$224.82	10.435%	$248.28	$248.28	$248.30	$248.30
Purchase #6	$59.50	4.303%	$62.0603	$62.06	$62.05	$62.10
Purchase #7	$41.60	10.565%	$45.995	$46.00	$46.00	$46.00
7 purchase totals =	$707.20		$763.7575	$763.76	$763.80	$763.90