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	$86.38	3.429%	$89.342	$89.34	$89.35	$89.30
Purchase #2	$227.73	7.316%	$244.3907	$244.39	$244.40	$244.40
Purchase #3	$123.39	13.735%	$140.3376	$140.34	$140.35	$140.30
Purchase #4	$68.99	5.162%	$72.5513	$72.55	$72.55	$72.60
Purchase #5	$161.50	7.845%	$174.1697	$174.17	$174.15	$174.20
Purchase #6	$98.78	13.350%	$111.9671	$111.97	$111.95	$112.00
Purchase #7	$97.68	10.349%	$107.7889	$107.79	$107.80	$107.80
7 purchase totals =	$864.45		$940.5473	$940.55	$940.55	$940.60