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	$208.76	5.528%	$220.3003	$220.30	$220.30	$220.30
Purchase #2	$189.62	7.345%	$203.5476	$203.55	$203.55	$203.50
Purchase #3	$89.82	13.385%	$101.8424	$101.84	$101.85	$101.80
Purchase #4	$166.51	12.395%	$187.1489	$187.15	$187.15	$187.10
Purchase #5	$160.49	5.280%	$168.9639	$168.96	$168.95	$169.00
Purchase #6	$97.96	13.417%	$111.1033	$111.10	$111.10	$111.10
Purchase #7	$231.81	13.390%	$262.8494	$262.85	$262.85	$262.80
7 purchase totals =	$1,144.97		$1,255.7558	$1,255.75	$1,255.75	$1,255.60