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	$84.67	13.546%	$96.1394	$96.14	$96.15	$96.10
Purchase #2	$106.79	4.742%	$111.854	$111.85	$111.85	$111.90
Purchase #3	$152.40	11.230%	$169.5145	$169.51	$169.50	$169.50
Purchase #4	$14.98	11.388%	$16.6859	$16.69	$16.70	$16.70
Purchase #5	$49.75	13.105%	$56.2697	$56.27	$56.25	$56.30
Purchase #6	$246.72	13.845%	$280.8784	$280.88	$280.90	$280.90
Purchase #7	$222.56	8.432%	$241.3263	$241.33	$241.35	$241.30
7 purchase totals =	$877.87		$972.6682	$972.67	$972.70	$972.70