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	$35.58	8.144%	$38.4776	$38.48	$38.50	$38.50
Purchase #2	$68.93	5.420%	$72.666	$72.67	$72.65	$72.70
Purchase #3	$211.90	7.542%	$227.8815	$227.88	$227.90	$227.90
Purchase #4	$238.32	6.504%	$253.8203	$253.82	$253.80	$253.80
Purchase #5	$206.89	8.205%	$223.8653	$223.87	$223.85	$223.90
Purchase #6	$234.40	4.421%	$244.7628	$244.76	$244.75	$244.80
Purchase #7	$173.50	6.617%	$184.9805	$184.98	$185.00	$185.00
7 purchase totals =	$1,169.52		$1,246.4540	$1,246.46	$1,246.45	$1,246.60