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	$101.60	6.854%	$108.5637	$108.56	$108.55	$108.60
Purchase #2	$55.46	13.370%	$62.875	$62.88	$62.90	$62.90
Purchase #3	$232.25	10.474%	$256.5759	$256.58	$256.60	$256.60
Purchase #4	$228.54	12.177%	$256.3693	$256.37	$256.35	$256.40
Purchase #5	$87.53	8.469%	$94.9429	$94.94	$94.95	$94.90
Purchase #6	$213.79	4.679%	$223.7932	$223.79	$223.80	$223.80
Purchase #7	$95.28	4.823%	$99.8754	$99.88	$99.90	$99.90
7 purchase totals =	$1,014.45		$1,102.9954	$1,103.00	$1,103.05	$1,103.10