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	$63.96	13.847%	$72.8165	$72.82	$72.80	$72.80
Purchase #2	$215.76	11.702%	$241.0082	$241.01	$241.00	$241.00
Purchase #3	$249.54	6.689%	$266.2317	$266.23	$266.25	$266.20
Purchase #4	$132.61	13.715%	$150.7975	$150.80	$150.80	$150.80
Purchase #5	$234.79	3.163%	$242.2164	$242.22	$242.20	$242.20
Purchase #6	$239.43	13.816%	$272.5096	$272.51	$272.50	$272.50
Purchase #7	$178.62	11.821%	$199.7347	$199.73	$199.75	$199.70
7 purchase totals =	$1,314.71		$1,445.3146	$1,445.32	$1,445.30	$1,445.20