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	$7.94	10.271%	$8.7555	$8.76	$8.75	$8.80
Purchase #2	$72.73	11.873%	$81.3652	$81.37	$81.35	$81.40
Purchase #3	$169.83	9.206%	$185.4645	$185.46	$185.45	$185.50
Purchase #4	$209.98	11.170%	$233.4348	$233.43	$233.45	$233.40
Purchase #5	$59.31	11.578%	$66.1769	$66.18	$66.20	$66.20
Purchase #6	$78.46	5.259%	$82.5862	$82.59	$82.60	$82.60
Purchase #7	$63.98	13.843%	$72.8368	$72.84	$72.85	$72.80
7 purchase totals =	$662.23		$730.6199	$730.63	$730.65	$730.70