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	$72.41	11.386%	$80.6546	$80.65	$80.65	$80.70
Purchase #2	$66.78	8.327%	$72.3408	$72.34	$72.35	$72.30
Purchase #3	$89.42	7.163%	$95.8252	$95.83	$95.85	$95.80
Purchase #4	$113.29	6.596%	$120.7626	$120.76	$120.75	$120.80
Purchase #5	$156.35	9.604%	$171.3659	$171.37	$171.35	$171.40
Purchase #6	$135.57	4.670%	$141.9011	$141.90	$141.90	$141.90
Purchase #7	$29.99	5.839%	$31.7411	$31.74	$31.75	$31.70
7 purchase totals =	$663.81		$714.5913	$714.59	$714.60	$714.60