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	$90.96	7.246%	$97.551	$97.55	$97.55	$97.60
Purchase #2	$159.33	9.266%	$174.0935	$174.09	$174.10	$174.10
Purchase #3	$68.59	6.166%	$72.8193	$72.82	$72.80	$72.80
Purchase #4	$185.42	8.128%	$200.4909	$200.49	$200.50	$200.50
Purchase #5	$59.60	12.194%	$66.8676	$66.87	$66.85	$66.90
Purchase #6	$6.63	3.380%	$6.8541	$6.85	$6.85	$6.90
Purchase #7	$245.75	9.561%	$269.2462	$269.25	$269.25	$269.20
7 purchase totals =	$816.28		$887.9226	$887.92	$887.90	$888.00