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	$239.64	13.440%	$271.8476	$271.85	$271.85	$271.80
Purchase #2	$152.43	6.375%	$162.1474	$162.15	$162.15	$162.10
Purchase #3	$237.28	12.452%	$266.8261	$266.83	$266.85	$266.80
Purchase #4	$208.85	4.794%	$218.8623	$218.86	$218.85	$218.90
Purchase #5	$137.71	4.756%	$144.2595	$144.26	$144.25	$144.30
Purchase #6	$205.94	8.672%	$223.7991	$223.80	$223.80	$223.80
Purchase #7	$91.76	5.645%	$96.9399	$96.94	$96.95	$96.90
7 purchase totals =	$1,273.61		$1,384.6819	$1,384.69	$1,384.70	$1,384.60