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	$55.40	6.537%	$59.0215	$59.02	$59.00	$59.00
Purchase #2	$193.40	11.362%	$215.3741	$215.37	$215.35	$215.40
Purchase #3	$163.58	10.557%	$180.8491	$180.85	$180.85	$180.80
Purchase #4	$11.81	9.620%	$12.9461	$12.95	$12.95	$12.90
Purchase #5	$56.54	10.822%	$62.6588	$62.66	$62.65	$62.70
Purchase #6	$234.32	4.406%	$244.6441	$244.64	$244.65	$244.60
Purchase #7	$56.48	8.872%	$61.4909	$61.49	$61.50	$61.50
7 purchase totals =	$771.53		$836.9846	$836.98	$836.95	$836.90