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	$218.85	10.304%	$241.4003	$241.40	$241.40	$241.40
Purchase #2	$60.47	3.175%	$62.3899	$62.39	$62.40	$62.40
Purchase #3	$7.30	6.745%	$7.7924	$7.79	$7.80	$7.80
Purchase #4	$190.48	3.260%	$196.6896	$196.69	$196.70	$196.70
Purchase #5	$225.80	12.678%	$254.4269	$254.43	$254.45	$254.40
Purchase #6	$137.69	3.439%	$142.4252	$142.43	$142.45	$142.40
Purchase #7	$219.47	9.411%	$240.1243	$240.12	$240.10	$240.10
7 purchase totals =	$1,060.06		$1,145.2486	$1,145.25	$1,145.30	$1,145.20