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	$40.37	5.779%	$42.703	$42.70	$42.70	$42.70
Purchase #2	$101.71	7.181%	$109.0138	$109.01	$109.00	$109.00
Purchase #3	$137.84	6.205%	$146.393	$146.39	$146.40	$146.40
Purchase #4	$122.45	4.481%	$127.937	$127.94	$127.95	$127.90
Purchase #5	$186.28	6.641%	$198.6509	$198.65	$198.65	$198.70
Purchase #6	$247.56	7.287%	$265.5997	$265.60	$265.60	$265.60
Purchase #7	$30.65	13.775%	$34.872	$34.87	$34.85	$34.90
7 purchase totals =	$866.86		$925.1694	$925.16	$925.15	$925.20