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	$163.37	13.524%	$185.4642	$185.46	$185.45	$185.50
Purchase #2	$168.87	7.688%	$181.8527	$181.85	$181.85	$181.90
Purchase #3	$45.58	7.214%	$48.8681	$48.87	$48.85	$48.90
Purchase #4	$175.34	3.857%	$182.1029	$182.10	$182.10	$182.10
Purchase #5	$66.64	10.754%	$73.8065	$73.81	$73.80	$73.80
Purchase #6	$76.67	7.680%	$82.5583	$82.56	$82.55	$82.60
Purchase #7	$16.58	13.276%	$18.7812	$18.78	$18.80	$18.80
7 purchase totals =	$713.05		$773.4339	$773.43	$773.40	$773.60