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	$105.71	9.351%	$115.5949	$115.59	$115.60	$115.60
Purchase #2	$177.26	6.873%	$189.4431	$189.44	$189.45	$189.40
Purchase #3	$145.89	5.759%	$154.2918	$154.29	$154.30	$154.30
Purchase #4	$105.75	10.370%	$116.7163	$116.72	$116.70	$116.70
Purchase #5	$72.56	6.674%	$77.4027	$77.40	$77.40	$77.40
Purchase #6	$89.36	11.684%	$99.8008	$99.80	$99.80	$99.80
Purchase #7	$172.64	3.730%	$179.0795	$179.08	$179.10	$179.10
7 purchase totals =	$869.17		$932.3291	$932.32	$932.35	$932.30