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	$85.40	9.501%	$93.5139	$93.51	$93.50	$93.50
Purchase #2	$65.42	9.815%	$71.841	$71.84	$71.85	$71.80
Purchase #3	$105.82	9.265%	$115.6242	$115.62	$115.60	$115.60
Purchase #4	$82.58	4.205%	$86.0525	$86.05	$86.05	$86.10
Purchase #5	$95.61	4.434%	$99.8493	$99.85	$99.85	$99.80
Purchase #6	$29.96	9.281%	$32.7406	$32.74	$32.75	$32.70
Purchase #7	$97.55	5.440%	$102.8567	$102.86	$102.85	$102.90
7 purchase totals =	$562.34		$602.4782	$602.47	$602.45	$602.40