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	$125.81	5.337%	$132.5245	$132.52	$132.50	$132.50
Purchase #2	$230.60	7.740%	$248.4484	$248.45	$248.45	$248.40
Purchase #3	$57.43	7.108%	$61.5121	$61.51	$61.50	$61.50
Purchase #4	$53.52	8.642%	$58.1452	$58.15	$58.15	$58.10
Purchase #5	$194.85	4.650%	$203.9105	$203.91	$203.90	$203.90
Purchase #6	$250.43	12.154%	$280.8673	$280.87	$280.85	$280.90
Purchase #7	$164.82	3.737%	$170.9793	$170.98	$171.00	$171.00
7 purchase totals =	$1,077.46		$1,156.3873	$1,156.39	$1,156.35	$1,156.30