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	$221.95	8.832%	$241.5526	$241.55	$241.55	$241.60
Purchase #2	$95.25	11.548%	$106.2495	$106.25	$106.25	$106.20
Purchase #3	$118.48	13.174%	$134.0886	$134.09	$134.10	$134.10
Purchase #4	$239.81	4.423%	$250.4168	$250.42	$250.40	$250.40
Purchase #5	$96.41	4.345%	$100.599	$100.60	$100.60	$100.60
Purchase #6	$50.63	13.681%	$57.5567	$57.56	$57.55	$57.60
Purchase #7	$122.96	4.162%	$128.0776	$128.08	$128.10	$128.10
7 purchase totals =	$945.49		$1,018.5408	$1,018.55	$1,018.55	$1,018.60