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	$174.78	6.499%	$186.139	$186.14	$186.15	$186.10
Purchase #2	$190.44	9.768%	$209.0422	$209.04	$209.05	$209.00
Purchase #3	$125.83	5.236%	$132.4185	$132.42	$132.40	$132.40
Purchase #4	$159.87	3.243%	$165.0546	$165.05	$165.05	$165.10
Purchase #5	$17.46	3.641%	$18.0957	$18.10	$18.10	$18.10
Purchase #6	$115.81	6.838%	$123.7291	$123.73	$123.75	$123.70
Purchase #7	$170.40	4.758%	$178.5076	$178.51	$178.50	$178.50
7 purchase totals =	$954.59		$1,012.9867	$1,012.99	$1,013.00	$1,012.90