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	$82.93	5.269%	$87.2996	$87.30	$87.30	$87.30
Purchase #2	$157.69	11.271%	$175.4632	$175.46	$175.45	$175.50
Purchase #3	$141.77	8.504%	$153.8261	$153.83	$153.85	$153.80
Purchase #4	$91.98	13.360%	$104.2685	$104.27	$104.25	$104.30
Purchase #5	$180.28	13.440%	$204.5096	$204.51	$204.50	$204.50
Purchase #6	$100.75	12.604%	$113.4485	$113.45	$113.45	$113.40
Purchase #7	$157.62	6.843%	$168.4059	$168.41	$168.40	$168.40
7 purchase totals =	$913.02		$1,007.2214	$1,007.23	$1,007.20	$1,007.20