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	$226.61	13.630%	$257.4969	$257.50	$257.50	$257.50
Purchase #2	$5.37	8.484%	$5.8256	$5.83	$5.85	$5.80
Purchase #3	$99.35	3.788%	$103.1134	$103.11	$103.10	$103.10
Purchase #4	$178.85	10.118%	$196.946	$196.95	$196.95	$196.90
Purchase #5	$166.42	9.570%	$182.3464	$182.35	$182.35	$182.30
Purchase #6	$55.30	13.563%	$62.8003	$62.80	$62.80	$62.80
Purchase #7	$93.51	10.865%	$103.6699	$103.67	$103.65	$103.70
7 purchase totals =	$825.41		$912.1985	$912.21	$912.20	$912.10