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	$99.27	5.122%	$104.3546	$104.35	$104.35	$104.40
Purchase #2	$56.95	8.591%	$61.8426	$61.84	$61.85	$61.80
Purchase #3	$54.25	10.202%	$59.7846	$59.78	$59.80	$59.80
Purchase #4	$232.94	10.264%	$256.849	$256.85	$256.85	$256.80
Purchase #5	$131.35	6.692%	$140.1399	$140.14	$140.15	$140.10
Purchase #6	$108.35	9.268%	$118.3919	$118.39	$118.40	$118.40
Purchase #7	$149.56	5.477%	$157.7514	$157.75	$157.75	$157.80
7 purchase totals =	$832.67		$899.1140	$899.10	$899.15	$899.10