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	$179.32	11.844%	$200.5587	$200.56	$200.55	$200.60
Purchase #2	$205.44	4.778%	$215.2559	$215.26	$215.25	$215.30
Purchase #3	$127.97	11.578%	$142.7864	$142.79	$142.80	$142.80
Purchase #4	$186.49	13.804%	$212.2331	$212.23	$212.25	$212.20
Purchase #5	$139.38	8.381%	$151.0614	$151.06	$151.05	$151.10
Purchase #6	$209.42	3.757%	$217.2879	$217.29	$217.30	$217.30
Purchase #7	$138.33	9.297%	$151.1905	$151.19	$151.20	$151.20
7 purchase totals =	$1,186.35		$1,290.3739	$1,290.38	$1,290.40	$1,290.50