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	$96.43	6.825%	$103.0113	$103.01	$103.00	$103.00
Purchase #2	$79.28	5.410%	$83.569	$83.57	$83.55	$83.60
Purchase #3	$227.45	5.725%	$240.4715	$240.47	$240.45	$240.50
Purchase #4	$225.67	13.703%	$256.5936	$256.59	$256.60	$256.60
Purchase #5	$187.28	10.368%	$206.6972	$206.70	$206.70	$206.70
Purchase #6	$91.77	9.633%	$100.6102	$100.61	$100.60	$100.60
Purchase #7	$181.32	9.144%	$197.8999	$197.90	$197.90	$197.90
7 purchase totals =	$1,089.20		$1,188.8527	$1,188.85	$1,188.80	$1,188.90