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	$217.73	3.351%	$225.0261	$225.03	$225.05	$225.00
Purchase #2	$142.66	13.688%	$162.1873	$162.19	$162.20	$162.20
Purchase #3	$125.90	3.327%	$130.0887	$130.09	$130.10	$130.10
Purchase #4	$85.64	6.112%	$90.8743	$90.87	$90.85	$90.90
Purchase #5	$46.64	4.569%	$48.771	$48.77	$48.75	$48.80
Purchase #6	$191.98	6.570%	$204.5931	$204.59	$204.60	$204.60
Purchase #7	$73.97	6.534%	$78.8032	$78.80	$78.80	$78.80
7 purchase totals =	$884.52		$940.3437	$940.34	$940.35	$940.40