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	$148.55	4.752%	$155.6091	$155.61	$155.60	$155.60
Purchase #2	$156.38	3.698%	$162.1629	$162.16	$162.15	$162.20
Purchase #3	$158.68	6.207%	$168.5293	$168.53	$168.55	$168.50
Purchase #4	$81.63	10.797%	$90.4436	$90.44	$90.45	$90.40
Purchase #5	$46.46	8.272%	$50.3032	$50.30	$50.30	$50.30
Purchase #6	$100.86	3.709%	$104.6009	$104.60	$104.60	$104.60
Purchase #7	$126.29	12.127%	$141.6052	$141.61	$141.60	$141.60
7 purchase totals =	$818.85		$873.2542	$873.25	$873.25	$873.20