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	$86.47	9.241%	$94.4607	$94.46	$94.45	$94.50
Purchase #2	$92.65	10.672%	$102.5376	$102.54	$102.55	$102.50
Purchase #3	$42.75	3.558%	$44.271	$44.27	$44.25	$44.30
Purchase #4	$62.51	8.161%	$67.6114	$67.61	$67.60	$67.60
Purchase #5	$139.81	6.229%	$148.5188	$148.52	$148.50	$148.50
Purchase #6	$176.95	13.849%	$201.4558	$201.46	$201.45	$201.50
Purchase #7	$225.61	3.431%	$233.3507	$233.35	$233.35	$233.40
7 purchase totals =	$826.75		$892.2060	$892.21	$892.15	$892.30