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	$100.29	9.442%	$109.7594	$109.76	$109.75	$109.80
Purchase #2	$103.70	3.701%	$107.5379	$107.54	$107.55	$107.50
Purchase #3	$65.69	8.735%	$71.428	$71.43	$71.45	$71.40
Purchase #4	$120.86	3.857%	$125.5216	$125.52	$125.50	$125.50
Purchase #5	$37.61	4.781%	$39.4081	$39.41	$39.40	$39.40
Purchase #6	$134.49	3.669%	$139.4244	$139.42	$139.40	$139.40
Purchase #7	$167.44	4.226%	$174.516	$174.52	$174.50	$174.50
7 purchase totals =	$730.08		$767.5954	$767.60	$767.55	$767.50