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	$158.62	5.581%	$167.4726	$167.47	$167.45	$167.50
Purchase #2	$46.39	13.123%	$52.4778	$52.48	$52.50	$52.50
Purchase #3	$145.77	12.519%	$164.0189	$164.02	$164.00	$164.00
Purchase #4	$168.98	3.791%	$175.386	$175.39	$175.40	$175.40
Purchase #5	$43.34	12.196%	$48.6257	$48.63	$48.65	$48.60
Purchase #6	$72.73	6.259%	$77.2822	$77.28	$77.30	$77.30
Purchase #7	$166.91	8.788%	$181.5781	$181.58	$181.60	$181.60
7 purchase totals =	$802.74		$866.8413	$866.85	$866.90	$866.90