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	$225.52	5.358%	$237.6034	$237.60	$237.60	$237.60
Purchase #2	$89.67	10.872%	$99.4189	$99.42	$99.40	$99.40
Purchase #3	$45.98	5.425%	$48.4744	$48.47	$48.45	$48.50
Purchase #4	$61.54	10.521%	$68.0146	$68.01	$68.00	$68.00
Purchase #5	$59.89	3.370%	$61.9083	$61.91	$61.90	$61.90
Purchase #6	$142.40	8.537%	$154.5567	$154.56	$154.55	$154.60
Purchase #7	$87.90	4.589%	$91.9337	$91.93	$91.95	$91.90
7 purchase totals =	$712.90		$761.9100	$761.90	$761.85	$761.90