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	$245.43	6.708%	$261.8934	$261.89	$261.90	$261.90
Purchase #2	$49.97	10.698%	$55.3158	$55.32	$55.30	$55.30
Purchase #3	$190.67	7.781%	$205.506	$205.51	$205.50	$205.50
Purchase #4	$195.85	3.573%	$202.8477	$202.85	$202.85	$202.80
Purchase #5	$142.78	13.704%	$162.3466	$162.35	$162.35	$162.30
Purchase #6	$187.81	4.527%	$196.3122	$196.31	$196.30	$196.30
Purchase #7	$241.71	5.728%	$255.5551	$255.56	$255.55	$255.60
7 purchase totals =	$1,254.22		$1,339.7768	$1,339.79	$1,339.75	$1,339.70