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	$183.33	9.518%	$200.7793	$200.78	$200.80	$200.80
Purchase #2	$38.99	6.599%	$41.563	$41.56	$41.55	$41.60
Purchase #3	$117.66	8.518%	$127.6823	$127.68	$127.70	$127.70
Purchase #4	$40.98	6.619%	$43.6925	$43.69	$43.70	$43.70
Purchase #5	$118.47	11.404%	$131.9803	$131.98	$132.00	$132.00
Purchase #6	$192.94	12.283%	$216.6388	$216.64	$216.65	$216.60
Purchase #7	$5.43	12.682%	$6.1186	$6.12	$6.10	$6.10
7 purchase totals =	$697.80		$768.4548	$768.45	$768.50	$768.50