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	$192.58	10.358%	$212.5274	$212.53	$212.55	$212.50
Purchase #2	$70.97	9.151%	$77.4645	$77.46	$77.45	$77.50
Purchase #3	$21.53	3.274%	$22.2349	$22.23	$22.25	$22.20
Purchase #4	$150.54	5.834%	$159.3225	$159.32	$159.30	$159.30
Purchase #5	$13.39	11.848%	$14.9764	$14.98	$15.00	$15.00
Purchase #6	$112.39	10.228%	$123.8852	$123.89	$123.90	$123.90
Purchase #7	$94.35	6.484%	$100.4677	$100.47	$100.45	$100.50
7 purchase totals =	$655.75		$710.8786	$710.88	$710.90	$710.90