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	$238.98	6.510%	$254.5376	$254.54	$254.55	$254.50
Purchase #2	$247.89	4.475%	$258.9831	$258.98	$259.00	$259.00
Purchase #3	$220.59	4.518%	$230.5563	$230.56	$230.55	$230.60
Purchase #4	$35.54	5.660%	$37.5516	$37.55	$37.55	$37.60
Purchase #5	$200.62	6.556%	$213.7726	$213.77	$213.75	$213.80
Purchase #6	$64.39	3.402%	$66.5805	$66.58	$66.60	$66.60
Purchase #7	$90.74	10.248%	$100.039	$100.04	$100.05	$100.00
7 purchase totals =	$1,098.75		$1,162.0207	$1,162.02	$1,162.05	$1,162.10