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	$98.33	7.557%	$105.7608	$105.76	$105.75	$105.80
Purchase #2	$131.52	6.323%	$139.836	$139.84	$139.85	$139.80
Purchase #3	$19.25	6.216%	$20.4466	$20.45	$20.45	$20.40
Purchase #4	$100.82	6.471%	$107.3441	$107.34	$107.35	$107.30
Purchase #5	$249.31	6.502%	$265.5201	$265.52	$265.50	$265.50
Purchase #6	$181.60	9.314%	$198.5142	$198.51	$198.50	$198.50
Purchase #7	$206.33	11.617%	$230.2994	$230.30	$230.30	$230.30
7 purchase totals =	$987.16		$1,067.7212	$1,067.72	$1,067.70	$1,067.60