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	$112.77	10.196%	$124.268	$124.27	$124.25	$124.30
Purchase #2	$72.86	11.805%	$81.4611	$81.46	$81.45	$81.50
Purchase #3	$32.33	8.752%	$35.1595	$35.16	$35.15	$35.20
Purchase #4	$60.48	5.391%	$63.7405	$63.74	$63.75	$63.70
Purchase #5	$36.85	12.401%	$41.4198	$41.42	$41.40	$41.40
Purchase #6	$157.33	5.838%	$166.5149	$166.51	$166.50	$166.50
Purchase #7	$104.51	7.449%	$112.2949	$112.29	$112.30	$112.30
7 purchase totals =	$577.13		$624.8587	$624.85	$624.80	$624.90