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	$153.73	7.676%	$165.5303	$165.53	$165.55	$165.50
Purchase #2	$144.42	10.271%	$159.2534	$159.25	$159.25	$159.30
Purchase #3	$75.80	12.564%	$85.3235	$85.32	$85.30	$85.30
Purchase #4	$93.80	8.649%	$101.9128	$101.91	$101.90	$101.90
Purchase #5	$96.46	9.440%	$105.5658	$105.57	$105.55	$105.60
Purchase #6	$13.59	12.469%	$15.2845	$15.28	$15.30	$15.30
Purchase #7	$111.43	4.804%	$116.7831	$116.78	$116.80	$116.80
7 purchase totals =	$689.23		$749.6534	$749.64	$749.65	$749.70