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	$185.93	7.504%	$199.8822	$199.88	$199.90	$199.90
Purchase #2	$27.83	13.446%	$31.572	$31.57	$31.55	$31.60
Purchase #3	$131.80	6.663%	$140.5818	$140.58	$140.60	$140.60
Purchase #4	$166.77	3.154%	$172.0299	$172.03	$172.05	$172.00
Purchase #5	$192.99	13.301%	$218.6596	$218.66	$218.65	$218.70
Purchase #6	$38.29	3.641%	$39.6841	$39.68	$39.70	$39.70
Purchase #7	$230.71	10.671%	$255.3291	$255.33	$255.35	$255.30
7 purchase totals =	$974.32		$1,057.7387	$1,057.73	$1,057.80	$1,057.80