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	$92.98	8.281%	$100.6797	$100.68	$100.70	$100.70
Purchase #2	$38.72	8.144%	$41.8734	$41.87	$41.85	$41.90
Purchase #3	$127.65	6.109%	$135.4481	$135.45	$135.45	$135.40
Purchase #4	$215.65	4.542%	$225.4448	$225.44	$225.45	$225.40
Purchase #5	$160.80	7.284%	$172.5127	$172.51	$172.50	$172.50
Purchase #6	$208.36	6.841%	$222.6139	$222.61	$222.60	$222.60
Purchase #7	$229.65	10.415%	$253.568	$253.57	$253.55	$253.60
7 purchase totals =	$1,073.81		$1,152.1406	$1,152.13	$1,152.10	$1,152.10