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	$218.63	9.239%	$238.8292	$238.83	$238.85	$238.80
Purchase #2	$105.63	5.139%	$111.0583	$111.06	$111.05	$111.10
Purchase #3	$59.77	7.835%	$64.453	$64.45	$64.45	$64.50
Purchase #4	$12.42	4.400%	$12.9665	$12.97	$12.95	$13.00
Purchase #5	$165.45	8.276%	$179.1426	$179.14	$179.15	$179.10
Purchase #6	$117.27	9.700%	$128.6452	$128.65	$128.65	$128.60
Purchase #7	$78.66	9.131%	$85.8424	$85.84	$85.85	$85.80
7 purchase totals =	$757.83		$820.9372	$820.94	$820.95	$820.90