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	$105.61	10.284%	$116.4709	$116.47	$116.45	$116.50
Purchase #2	$139.78	9.261%	$152.725	$152.73	$152.75	$152.70
Purchase #3	$59.74	6.386%	$63.555	$63.56	$63.55	$63.60
Purchase #4	$118.53	6.788%	$126.5758	$126.58	$126.60	$126.60
Purchase #5	$190.72	5.323%	$200.872	$200.87	$200.85	$200.90
Purchase #6	$136.35	4.817%	$142.918	$142.92	$142.90	$142.90
Purchase #7	$52.61	4.808%	$55.1395	$55.14	$55.15	$55.10
7 purchase totals =	$803.34		$858.2562	$858.27	$858.25	$858.30