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	$38.58	13.618%	$43.8338	$43.83	$43.85	$43.80
Purchase #2	$233.71	7.120%	$250.3502	$250.35	$250.35	$250.40
Purchase #3	$54.29	4.263%	$56.6044	$56.60	$56.60	$56.60
Purchase #4	$127.60	9.503%	$139.7258	$139.73	$139.75	$139.70
Purchase #5	$217.97	13.272%	$246.899	$246.90	$246.90	$246.90
Purchase #6	$92.90	5.480%	$97.9909	$97.99	$98.00	$98.00
Purchase #7	$247.50	13.476%	$280.8531	$280.85	$280.85	$280.90
7 purchase totals =	$1,012.55		$1,116.2572	$1,116.25	$1,116.30	$1,116.30