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	$144.62	4.834%	$151.6109	$151.61	$151.60	$151.60
Purchase #2	$118.50	11.271%	$131.8561	$131.86	$131.85	$131.90
Purchase #3	$79.64	5.258%	$83.8275	$83.83	$83.85	$83.80
Purchase #4	$164.34	3.391%	$169.9128	$169.91	$169.90	$169.90
Purchase #5	$17.64	12.577%	$19.8586	$19.86	$19.85	$19.90
Purchase #6	$130.55	6.818%	$139.4509	$139.45	$139.45	$139.50
Purchase #7	$25.64	5.858%	$27.142	$27.14	$27.15	$27.10
7 purchase totals =	$680.93		$723.6588	$723.66	$723.65	$723.70