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	$172.32	13.383%	$195.3816	$195.38	$195.40	$195.40
Purchase #2	$105.55	13.758%	$120.0716	$120.07	$120.05	$120.10
Purchase #3	$234.48	3.395%	$242.4406	$242.44	$242.45	$242.40
Purchase #4	$125.73	11.524%	$140.2191	$140.22	$140.20	$140.20
Purchase #5	$174.86	6.145%	$185.6051	$185.61	$185.60	$185.60
Purchase #6	$63.38	5.302%	$66.7404	$66.74	$66.75	$66.70
Purchase #7	$139.79	11.233%	$155.4926	$155.49	$155.50	$155.50
7 purchase totals =	$1,016.11		$1,105.9510	$1,105.95	$1,105.95	$1,105.90