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	$191.42	13.122%	$216.5381	$216.54	$216.55	$216.50
Purchase #2	$15.40	6.831%	$16.452	$16.45	$16.45	$16.50
Purchase #3	$149.81	12.535%	$168.5887	$168.59	$168.60	$168.60
Purchase #4	$193.31	3.404%	$199.8903	$199.89	$199.90	$199.90
Purchase #5	$51.25	3.605%	$53.0976	$53.10	$53.10	$53.10
Purchase #6	$222.35	10.627%	$245.9791	$245.98	$246.00	$246.00
Purchase #7	$164.57	9.694%	$180.5234	$180.52	$180.50	$180.50
7 purchase totals =	$988.11		$1,081.0692	$1,081.07	$1,081.10	$1,081.10