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	$60.37	7.115%	$64.6653	$64.67	$64.65	$64.70
Purchase #2	$210.76	6.677%	$224.8324	$224.83	$224.85	$224.80
Purchase #3	$151.30	4.641%	$158.3218	$158.32	$158.30	$158.30
Purchase #4	$234.51	11.527%	$261.542	$261.54	$261.55	$261.50
Purchase #5	$90.94	4.244%	$94.7995	$94.80	$94.80	$94.80
Purchase #6	$225.54	9.755%	$247.5414	$247.54	$247.55	$247.50
Purchase #7	$92.46	12.331%	$103.8612	$103.86	$103.85	$103.90
7 purchase totals =	$1,065.88		$1,155.5636	$1,155.56	$1,155.55	$1,155.50