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	$160.26	7.756%	$172.6898	$172.69	$172.70	$172.70
Purchase #2	$225.28	13.538%	$255.7784	$255.78	$255.80	$255.80
Purchase #3	$164.85	12.760%	$185.8849	$185.88	$185.90	$185.90
Purchase #4	$59.52	9.629%	$65.2512	$65.25	$65.25	$65.30
Purchase #5	$81.45	7.649%	$87.6801	$87.68	$87.70	$87.70
Purchase #6	$74.68	8.736%	$81.204	$81.20	$81.20	$81.20
Purchase #7	$166.78	9.458%	$182.5541	$182.55	$182.55	$182.60
7 purchase totals =	$932.82		$1,031.0425	$1,031.03	$1,031.10	$1,031.20