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	$151.85	10.543%	$167.8595	$167.86	$167.85	$167.90
Purchase #2	$97.98	11.550%	$109.2967	$109.30	$109.30	$109.30
Purchase #3	$85.82	9.103%	$93.6322	$93.63	$93.65	$93.60
Purchase #4	$209.46	13.278%	$237.2721	$237.27	$237.25	$237.30
Purchase #5	$14.92	6.631%	$15.9093	$15.91	$15.90	$15.90
Purchase #6	$15.74	11.784%	$17.5948	$17.59	$17.60	$17.60
Purchase #7	$86.82	3.414%	$89.784	$89.78	$89.80	$89.80
7 purchase totals =	$662.59		$731.3486	$731.34	$731.35	$731.40