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	$183.89	8.739%	$199.9601	$199.96	$199.95	$200.00
Purchase #2	$229.90	11.480%	$256.2925	$256.29	$256.30	$256.30
Purchase #3	$21.51	3.353%	$22.2312	$22.23	$22.25	$22.20
Purchase #4	$199.58	12.790%	$225.1063	$225.11	$225.10	$225.10
Purchase #5	$239.72	4.375%	$250.2078	$250.21	$250.20	$250.20
Purchase #6	$41.38	12.571%	$46.5819	$46.58	$46.60	$46.60
Purchase #7	$72.98	12.379%	$82.0142	$82.01	$82.00	$82.00
7 purchase totals =	$988.96		$1,082.3940	$1,082.39	$1,082.40	$1,082.40