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	$227.50	12.486%	$255.9057	$255.91	$255.90	$255.90
Purchase #2	$40.76	6.423%	$43.378	$43.38	$43.40	$43.40
Purchase #3	$124.81	9.167%	$136.2513	$136.25	$136.25	$136.30
Purchase #4	$189.82	13.338%	$215.1382	$215.14	$215.15	$215.10
Purchase #5	$197.34	13.403%	$223.7895	$223.79	$223.80	$223.80
Purchase #6	$148.77	13.370%	$168.6605	$168.66	$168.65	$168.70
Purchase #7	$55.48	12.804%	$62.5837	$62.58	$62.60	$62.60
7 purchase totals =	$984.48		$1,105.7069	$1,105.71	$1,105.75	$1,105.80