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	$168.59	5.734%	$178.257	$178.26	$178.25	$178.30
Purchase #2	$102.74	13.442%	$116.5503	$116.55	$116.55	$116.60
Purchase #3	$10.81	7.117%	$11.5793	$11.58	$11.60	$11.60
Purchase #4	$101.65	3.851%	$105.5645	$105.56	$105.55	$105.60
Purchase #5	$25.97	9.297%	$28.3844	$28.38	$28.40	$28.40
Purchase #6	$137.77	7.358%	$147.9071	$147.91	$147.90	$147.90
Purchase #7	$238.25	11.605%	$265.8989	$265.90	$265.90	$265.90
7 purchase totals =	$785.78		$854.1415	$854.14	$854.15	$854.30