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	$111.38	4.120%	$115.9689	$115.97	$115.95	$116.00
Purchase #2	$172.88	13.833%	$196.7945	$196.79	$196.80	$196.80
Purchase #3	$195.30	5.188%	$205.4322	$205.43	$205.45	$205.40
Purchase #4	$173.58	12.405%	$195.1126	$195.11	$195.10	$195.10
Purchase #5	$133.97	8.797%	$145.7553	$145.76	$145.75	$145.80
Purchase #6	$62.41	8.834%	$67.9233	$67.92	$67.90	$67.90
Purchase #7	$150.35	4.105%	$156.5219	$156.52	$156.50	$156.50
7 purchase totals =	$999.87		$1,083.5087	$1,083.50	$1,083.45	$1,083.50