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	$219.28	10.789%	$242.9381	$242.94	$242.95	$242.90
Purchase #2	$84.75	5.291%	$89.2341	$89.23	$89.25	$89.20
Purchase #3	$65.38	5.304%	$68.8478	$68.85	$68.85	$68.80
Purchase #4	$246.88	3.835%	$256.3478	$256.35	$256.35	$256.30
Purchase #5	$167.76	6.307%	$178.3406	$178.34	$178.35	$178.30
Purchase #6	$89.82	3.844%	$93.2727	$93.27	$93.25	$93.30
Purchase #7	$87.77	4.746%	$91.9356	$91.94	$91.95	$91.90
7 purchase totals =	$961.64		$1,020.9167	$1,020.92	$1,020.95	$1,020.70