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	$198.63	7.661%	$213.847	$213.85	$213.85	$213.80
Purchase #2	$134.88	7.116%	$144.4781	$144.48	$144.50	$144.50
Purchase #3	$97.80	3.469%	$101.1927	$101.19	$101.20	$101.20
Purchase #4	$225.57	13.320%	$255.6159	$255.62	$255.60	$255.60
Purchase #5	$21.73	4.854%	$22.7848	$22.78	$22.80	$22.80
Purchase #6	$104.89	6.326%	$111.5253	$111.53	$111.55	$111.50
Purchase #7	$65.37	5.136%	$68.7274	$68.73	$68.75	$68.70
7 purchase totals =	$848.87		$918.1712	$918.18	$918.25	$918.10