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	$54.43	8.479%	$59.0451	$59.05	$59.05	$59.00
Purchase #2	$81.79	11.105%	$90.8728	$90.87	$90.85	$90.90
Purchase #3	$92.30	4.310%	$96.2781	$96.28	$96.30	$96.30
Purchase #4	$249.47	3.686%	$258.6655	$258.67	$258.65	$258.70
Purchase #5	$110.56	6.600%	$117.857	$117.86	$117.85	$117.90
Purchase #6	$211.51	4.626%	$221.2945	$221.29	$221.30	$221.30
Purchase #7	$152.29	8.152%	$164.7047	$164.70	$164.70	$164.70
7 purchase totals =	$952.35		$1,008.7177	$1,008.72	$1,008.70	$1,008.80