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	$58.31	3.579%	$60.3969	$60.40	$60.40	$60.40
Purchase #2	$7.58	6.781%	$8.094	$8.09	$8.10	$8.10
Purchase #3	$74.86	7.360%	$80.3697	$80.37	$80.35	$80.40
Purchase #4	$58.79	10.260%	$64.8219	$64.82	$64.80	$64.80
Purchase #5	$37.78	7.212%	$40.5047	$40.50	$40.50	$40.50
Purchase #6	$176.47	11.401%	$196.5893	$196.59	$196.60	$196.60
Purchase #7	$204.64	4.506%	$213.8611	$213.86	$213.85	$213.90
7 purchase totals =	$618.43		$664.6376	$664.63	$664.60	$664.70