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	$7.55	5.217%	$7.9439	$7.94	$7.95	$7.90
Purchase #2	$164.74	12.802%	$185.83	$185.83	$185.85	$185.80
Purchase #3	$83.39	9.159%	$91.0277	$91.03	$91.05	$91.00
Purchase #4	$239.64	12.543%	$269.698	$269.70	$269.70	$269.70
Purchase #5	$74.51	3.152%	$76.8586	$76.86	$76.85	$76.90
Purchase #6	$117.92	11.189%	$131.1141	$131.11	$131.10	$131.10
Purchase #7	$152.35	6.418%	$162.1278	$162.13	$162.15	$162.10
7 purchase totals =	$840.10		$924.6001	$924.60	$924.65	$924.50