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	$144.34	9.792%	$158.4738	$158.47	$158.45	$158.50
Purchase #2	$80.28	8.688%	$87.2547	$87.25	$87.25	$87.30
Purchase #3	$18.66	8.610%	$20.2666	$20.27	$20.25	$20.30
Purchase #4	$123.77	5.131%	$130.1206	$130.12	$130.10	$130.10
Purchase #5	$119.54	10.295%	$131.8466	$131.85	$131.85	$131.80
Purchase #6	$95.45	10.307%	$105.288	$105.29	$105.30	$105.30
Purchase #7	$108.55	6.737%	$115.863	$115.86	$115.85	$115.90
7 purchase totals =	$690.59		$749.1133	$749.11	$749.05	$749.20