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	$176.33	11.638%	$196.8513	$196.85	$196.85	$196.90
Purchase #2	$171.91	7.216%	$184.315	$184.32	$184.30	$184.30
Purchase #3	$90.87	9.601%	$99.5944	$99.59	$99.60	$99.60
Purchase #4	$245.50	6.520%	$261.5066	$261.51	$261.50	$261.50
Purchase #5	$20.75	9.162%	$22.6511	$22.65	$22.65	$22.70
Purchase #6	$122.34	11.119%	$135.943	$135.94	$135.95	$135.90
Purchase #7	$13.43	11.248%	$14.9406	$14.94	$14.95	$14.90
7 purchase totals =	$841.13		$915.8020	$915.80	$915.80	$915.80