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	$146.68	13.630%	$166.6725	$166.67	$166.65	$166.70
Purchase #2	$244.73	4.495%	$255.7306	$255.73	$255.75	$255.70
Purchase #3	$32.26	10.255%	$35.5683	$35.57	$35.55	$35.60
Purchase #4	$134.94	13.304%	$152.8924	$152.89	$152.90	$152.90
Purchase #5	$98.45	3.151%	$101.5522	$101.55	$101.55	$101.60
Purchase #6	$139.77	6.159%	$148.3784	$148.38	$148.40	$148.40
Purchase #7	$131.78	12.546%	$148.3131	$148.31	$148.30	$148.30
7 purchase totals =	$928.61		$1,009.1075	$1,009.10	$1,009.10	$1,009.20