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	$50.54	10.474%	$55.8336	$55.83	$55.85	$55.80
Purchase #2	$7.28	4.177%	$7.5841	$7.58	$7.60	$7.60
Purchase #3	$19.41	10.210%	$21.3918	$21.39	$21.40	$21.40
Purchase #4	$95.60	8.357%	$103.5893	$103.59	$103.60	$103.60
Purchase #5	$164.81	6.468%	$175.4699	$175.47	$175.45	$175.50
Purchase #6	$77.71	7.421%	$83.4769	$83.48	$83.50	$83.50
Purchase #7	$57.43	6.495%	$61.1601	$61.16	$61.15	$61.20
7 purchase totals =	$472.78		$508.5057	$508.50	$508.55	$508.60