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	$31.42	9.501%	$34.4052	$34.41	$34.40	$34.40
Purchase #2	$208.57	12.414%	$234.4619	$234.46	$234.45	$234.50
Purchase #3	$240.39	7.135%	$257.5418	$257.54	$257.55	$257.50
Purchase #4	$79.25	12.835%	$89.4217	$89.42	$89.40	$89.40
Purchase #5	$149.42	12.136%	$167.5536	$167.55	$167.55	$167.60
Purchase #6	$227.67	5.623%	$240.4719	$240.47	$240.45	$240.50
Purchase #7	$151.50	8.510%	$164.3927	$164.39	$164.40	$164.40
7 purchase totals =	$1,088.22		$1,188.2488	$1,188.24	$1,188.20	$1,188.30