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	$137.32	3.360%	$141.934	$141.93	$141.95	$141.90
Purchase #2	$12.60	9.133%	$13.7508	$13.75	$13.75	$13.80
Purchase #3	$9.82	3.446%	$10.1584	$10.16	$10.15	$10.20
Purchase #4	$112.94	3.444%	$116.8297	$116.83	$116.85	$116.80
Purchase #5	$182.53	3.251%	$188.4641	$188.46	$188.45	$188.50
Purchase #6	$200.81	4.509%	$209.8645	$209.86	$209.85	$209.90
Purchase #7	$129.76	7.397%	$139.3583	$139.36	$139.35	$139.40
7 purchase totals =	$785.78		$820.3598	$820.35	$820.35	$820.50