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	$208.34	5.423%	$219.6383	$219.64	$219.65	$219.60
Purchase #2	$179.89	10.792%	$199.3037	$199.30	$199.30	$199.30
Purchase #3	$68.48	3.288%	$70.7316	$70.73	$70.75	$70.70
Purchase #4	$8.89	12.835%	$10.031	$10.03	$10.05	$10.00
Purchase #5	$55.48	9.509%	$60.7556	$60.76	$60.75	$60.80
Purchase #6	$241.68	13.263%	$273.734	$273.73	$273.75	$273.70
Purchase #7	$151.56	10.783%	$167.9027	$167.90	$167.90	$167.90
7 purchase totals =	$914.32		$1,002.0969	$1,002.09	$1,002.15	$1,002.00