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	$192.71	13.547%	$218.8164	$218.82	$218.80	$218.80
Purchase #2	$59.89	7.204%	$64.2045	$64.20	$64.20	$64.20
Purchase #3	$15.55	6.353%	$16.5379	$16.54	$16.55	$16.50
Purchase #4	$129.83	3.666%	$134.5896	$134.59	$134.60	$134.60
Purchase #5	$28.25	13.855%	$32.164	$32.16	$32.15	$32.20
Purchase #6	$227.82	6.355%	$242.298	$242.30	$242.30	$242.30
Purchase #7	$19.78	7.655%	$21.2942	$21.29	$21.30	$21.30
7 purchase totals =	$673.83		$729.9046	$729.90	$729.90	$729.90