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	$76.32	9.602%	$83.6482	$83.65	$83.65	$83.60
Purchase #2	$125.55	13.462%	$142.4515	$142.45	$142.45	$142.50
Purchase #3	$196.45	9.143%	$214.4114	$214.41	$214.40	$214.40
Purchase #4	$169.37	12.687%	$190.858	$190.86	$190.85	$190.90
Purchase #5	$161.87	3.668%	$167.8074	$167.81	$167.80	$167.80
Purchase #6	$167.90	8.638%	$182.4032	$182.40	$182.40	$182.40
Purchase #7	$119.30	6.213%	$126.7121	$126.71	$126.70	$126.70
7 purchase totals =	$1,016.76		$1,108.2918	$1,108.29	$1,108.25	$1,108.30