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	$95.86	7.480%	$103.0303	$103.03	$103.05	$103.00
Purchase #2	$35.69	3.795%	$37.0444	$37.04	$37.05	$37.00
Purchase #3	$124.69	13.510%	$141.5356	$141.54	$141.55	$141.50
Purchase #4	$41.72	13.834%	$47.4915	$47.49	$47.50	$47.50
Purchase #5	$104.92	11.199%	$116.67	$116.67	$116.65	$116.70
Purchase #6	$241.80	5.577%	$255.2852	$255.29	$255.30	$255.30
Purchase #7	$121.90	10.414%	$134.5947	$134.59	$134.60	$134.60
7 purchase totals =	$766.58		$835.6517	$835.65	$835.70	$835.60