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	$54.80	9.755%	$60.1457	$60.15	$60.15	$60.10
Purchase #2	$55.37	5.717%	$58.5355	$58.54	$58.55	$58.50
Purchase #3	$95.33	10.753%	$105.5808	$105.58	$105.60	$105.60
Purchase #4	$241.60	10.869%	$267.8595	$267.86	$267.85	$267.90
Purchase #5	$32.91	9.382%	$35.9976	$36.00	$36.00	$36.00
Purchase #6	$166.48	11.593%	$185.78	$185.78	$185.80	$185.80
Purchase #7	$209.64	8.461%	$227.3776	$227.38	$227.40	$227.40
7 purchase totals =	$856.13		$941.2767	$941.29	$941.35	$941.30