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	$162.84	13.744%	$185.2207	$185.22	$185.20	$185.20
Purchase #2	$208.36	4.434%	$217.5987	$217.60	$217.60	$217.60
Purchase #3	$47.95	12.470%	$53.9294	$53.93	$53.95	$53.90
Purchase #4	$224.91	10.485%	$248.4918	$248.49	$248.50	$248.50
Purchase #5	$136.91	3.190%	$141.2774	$141.28	$141.30	$141.30
Purchase #6	$49.35	6.678%	$52.6456	$52.65	$52.65	$52.60
Purchase #7	$37.47	13.817%	$42.6472	$42.65	$42.65	$42.60
7 purchase totals =	$867.79		$941.8108	$941.82	$941.85	$941.70