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	$147.86	10.504%	$163.3912	$163.39	$163.40	$163.40
Purchase #2	$148.47	8.698%	$161.3839	$161.38	$161.40	$161.40
Purchase #3	$207.30	12.477%	$233.1648	$233.16	$233.15	$233.20
Purchase #4	$91.27	10.122%	$100.5083	$100.51	$100.50	$100.50
Purchase #5	$56.70	5.545%	$59.844	$59.84	$59.85	$59.80
Purchase #6	$109.32	9.187%	$119.3632	$119.36	$119.35	$119.40
Purchase #7	$7.35	7.193%	$7.8787	$7.88	$7.90	$7.90
7 purchase totals =	$768.27		$845.5341	$845.52	$845.55	$845.60