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	$28.55	3.870%	$29.6549	$29.65	$29.65	$29.70
Purchase #2	$154.68	6.432%	$164.629	$164.63	$164.65	$164.60
Purchase #3	$25.98	12.692%	$29.2774	$29.28	$29.30	$29.30
Purchase #4	$248.73	3.257%	$256.8311	$256.83	$256.85	$256.80
Purchase #5	$82.40	10.792%	$91.2926	$91.29	$91.30	$91.30
Purchase #6	$100.53	9.189%	$109.7677	$109.77	$109.75	$109.80
Purchase #7	$19.54	11.466%	$21.7805	$21.78	$21.80	$21.80
7 purchase totals =	$660.41		$703.2332	$703.23	$703.30	$703.30