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	$180.25	4.151%	$187.7322	$187.73	$187.75	$187.70
Purchase #2	$83.89	7.588%	$90.2556	$90.26	$90.25	$90.30
Purchase #3	$179.38	9.798%	$196.9557	$196.96	$196.95	$197.00
Purchase #4	$53.42	7.223%	$57.2785	$57.28	$57.30	$57.30
Purchase #5	$128.77	3.253%	$132.9589	$132.96	$132.95	$133.00
Purchase #6	$64.43	12.651%	$72.581	$72.58	$72.60	$72.60
Purchase #7	$209.86	13.234%	$237.6329	$237.63	$237.65	$237.60
7 purchase totals =	$900.00		$975.3948	$975.40	$975.45	$975.50