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	$128.97	6.703%	$137.6149	$137.61	$137.60	$137.60
Purchase #2	$142.43	7.626%	$153.2917	$153.29	$153.30	$153.30
Purchase #3	$125.61	13.289%	$142.3023	$142.30	$142.30	$142.30
Purchase #4	$73.90	13.530%	$83.8987	$83.90	$83.90	$83.90
Purchase #5	$107.94	5.322%	$113.6846	$113.68	$113.70	$113.70
Purchase #6	$128.54	12.280%	$144.3247	$144.32	$144.30	$144.30
Purchase #7	$240.73	13.149%	$272.3836	$272.38	$272.40	$272.40
7 purchase totals =	$948.12		$1,047.5005	$1,047.48	$1,047.50	$1,047.50