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	$207.61	5.230%	$218.468	$218.47	$218.45	$218.50
Purchase #2	$97.34	12.557%	$109.563	$109.56	$109.55	$109.60
Purchase #3	$203.41	11.870%	$227.5548	$227.55	$227.55	$227.60
Purchase #4	$89.71	6.608%	$95.638	$95.64	$95.65	$95.60
Purchase #5	$33.43	3.472%	$34.5907	$34.59	$34.60	$34.60
Purchase #6	$199.47	8.845%	$217.1131	$217.11	$217.10	$217.10
Purchase #7	$70.66	11.163%	$78.5478	$78.55	$78.55	$78.50
7 purchase totals =	$901.63		$981.4754	$981.47	$981.45	$981.50