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	$40.98	11.197%	$45.5685	$45.57	$45.55	$45.60
Purchase #2	$56.45	10.138%	$62.1729	$62.17	$62.15	$62.20
Purchase #3	$234.26	9.390%	$256.257	$256.26	$256.25	$256.30
Purchase #4	$85.44	5.138%	$89.8299	$89.83	$89.85	$89.80
Purchase #5	$164.96	5.466%	$173.9767	$173.98	$174.00	$174.00
Purchase #6	$112.28	6.285%	$119.3368	$119.34	$119.35	$119.30
Purchase #7	$222.35	7.747%	$239.5755	$239.58	$239.60	$239.60
7 purchase totals =	$916.72		$986.7173	$986.73	$986.75	$986.80