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	$90.79	5.190%	$95.502	$95.50	$95.50	$95.50
Purchase #2	$83.93	8.326%	$90.918	$90.92	$90.90	$90.90
Purchase #3	$72.96	12.401%	$82.0078	$82.01	$82.00	$82.00
Purchase #4	$220.45	4.541%	$230.4606	$230.46	$230.45	$230.50
Purchase #5	$77.44	12.854%	$87.3941	$87.39	$87.40	$87.40
Purchase #6	$198.96	13.135%	$225.0934	$225.09	$225.10	$225.10
Purchase #7	$111.38	11.649%	$124.3547	$124.35	$124.35	$124.40
7 purchase totals =	$855.91		$935.7306	$935.72	$935.70	$935.80