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	$56.28	9.195%	$61.4549	$61.45	$61.45	$61.50
Purchase #2	$112.45	5.659%	$118.8135	$118.81	$118.80	$118.80
Purchase #3	$24.35	4.799%	$25.5186	$25.52	$25.50	$25.50
Purchase #4	$227.83	12.679%	$256.7166	$256.72	$256.70	$256.70
Purchase #5	$239.69	10.746%	$265.4471	$265.45	$265.45	$265.40
Purchase #6	$232.63	5.272%	$244.8943	$244.89	$244.90	$244.90
Purchase #7	$149.56	13.572%	$169.8583	$169.86	$169.85	$169.90
7 purchase totals =	$1,042.79		$1,142.7033	$1,142.70	$1,142.65	$1,142.70