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	$140.74	8.304%	$152.427	$152.43	$152.45	$152.40
Purchase #2	$126.38	5.356%	$133.1489	$133.15	$133.15	$133.10
Purchase #3	$26.36	5.364%	$27.774	$27.77	$27.75	$27.80
Purchase #4	$76.37	8.490%	$82.8538	$82.85	$82.85	$82.90
Purchase #5	$238.71	4.143%	$248.5998	$248.60	$248.60	$248.60
Purchase #6	$244.75	10.268%	$269.8809	$269.88	$269.90	$269.90
Purchase #7	$110.40	7.382%	$118.5497	$118.55	$118.55	$118.50
7 purchase totals =	$963.71		$1,033.2341	$1,033.23	$1,033.25	$1,033.20