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	$79.60	7.314%	$85.4219	$85.42	$85.40	$85.40
Purchase #2	$210.74	13.429%	$239.0403	$239.04	$239.05	$239.00
Purchase #3	$19.28	10.781%	$21.3586	$21.36	$21.35	$21.40
Purchase #4	$187.51	5.821%	$198.425	$198.43	$198.45	$198.40
Purchase #5	$86.32	3.509%	$89.349	$89.35	$89.35	$89.30
Purchase #6	$248.45	10.327%	$274.1074	$274.11	$274.10	$274.10
Purchase #7	$129.50	5.742%	$136.9359	$136.94	$136.95	$136.90
7 purchase totals =	$961.40		$1,044.6381	$1,044.65	$1,044.65	$1,044.50