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	$149.77	12.540%	$168.5512	$168.55	$168.55	$168.60
Purchase #2	$142.46	4.285%	$148.5644	$148.56	$148.55	$148.60
Purchase #3	$133.97	11.154%	$148.913	$148.91	$148.90	$148.90
Purchase #4	$110.63	5.566%	$116.7877	$116.79	$116.80	$116.80
Purchase #5	$29.66	12.184%	$33.2738	$33.27	$33.25	$33.30
Purchase #6	$242.28	5.543%	$255.7096	$255.71	$255.70	$255.70
Purchase #7	$76.55	3.609%	$79.3127	$79.31	$79.30	$79.30
7 purchase totals =	$885.32		$951.1124	$951.10	$951.05	$951.20