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	$95.75	10.164%	$105.482	$105.48	$105.50	$105.50
Purchase #2	$164.98	11.151%	$183.3769	$183.38	$183.40	$183.40
Purchase #3	$100.85	6.574%	$107.4799	$107.48	$107.50	$107.50
Purchase #4	$85.31	6.115%	$90.5267	$90.53	$90.55	$90.50
Purchase #5	$154.40	8.658%	$167.768	$167.77	$167.75	$167.80
Purchase #6	$81.41	4.688%	$85.2265	$85.23	$85.25	$85.20
Purchase #7	$207.48	13.171%	$234.8072	$234.81	$234.80	$234.80
7 purchase totals =	$890.18		$974.6672	$974.68	$974.75	$974.70