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	$117.76	8.364%	$127.6094	$127.61	$127.60	$127.60
Purchase #2	$165.40	9.115%	$180.4762	$180.48	$180.50	$180.50
Purchase #3	$194.60	4.259%	$202.888	$202.89	$202.90	$202.90
Purchase #4	$182.65	10.776%	$202.3324	$202.33	$202.35	$202.30
Purchase #5	$139.85	11.829%	$156.3929	$156.39	$156.40	$156.40
Purchase #6	$92.43	6.471%	$98.4111	$98.41	$98.40	$98.40
Purchase #7	$40.89	7.183%	$43.8271	$43.83	$43.85	$43.80
7 purchase totals =	$933.58		$1,011.9371	$1,011.94	$1,012.00	$1,011.90