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	$226.48	7.597%	$243.6857	$243.69	$243.70	$243.70
Purchase #2	$111.44	10.861%	$123.5435	$123.54	$123.55	$123.50
Purchase #3	$29.82	10.430%	$32.9302	$32.93	$32.95	$32.90
Purchase #4	$137.31	12.767%	$154.8404	$154.84	$154.85	$154.80
Purchase #5	$66.50	9.310%	$72.6912	$72.69	$72.70	$72.70
Purchase #6	$137.96	7.531%	$148.3498	$148.35	$148.35	$148.30
Purchase #7	$224.95	13.238%	$254.7289	$254.73	$254.75	$254.70
7 purchase totals =	$934.46		$1,030.7697	$1,030.77	$1,030.85	$1,030.60