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	$67.57	6.682%	$72.085	$72.09	$72.10	$72.10
Purchase #2	$35.56	5.522%	$37.5236	$37.52	$37.50	$37.50
Purchase #3	$151.30	10.155%	$166.6645	$166.66	$166.65	$166.70
Purchase #4	$72.94	10.298%	$80.4514	$80.45	$80.45	$80.50
Purchase #5	$226.85	5.601%	$239.5559	$239.56	$239.55	$239.60
Purchase #6	$232.68	7.784%	$250.7918	$250.79	$250.80	$250.80
Purchase #7	$204.99	7.541%	$220.4483	$220.45	$220.45	$220.40
7 purchase totals =	$991.89		$1,067.5205	$1,067.52	$1,067.50	$1,067.60