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	$111.57	9.552%	$122.2272	$122.23	$122.25	$122.20
Purchase #2	$133.86	8.603%	$145.376	$145.38	$145.40	$145.40
Purchase #3	$83.72	7.107%	$89.67	$89.67	$89.65	$89.70
Purchase #4	$221.72	4.233%	$231.1054	$231.11	$231.10	$231.10
Purchase #5	$108.27	3.799%	$112.3832	$112.38	$112.40	$112.40
Purchase #6	$190.80	4.475%	$199.3383	$199.34	$199.35	$199.30
Purchase #7	$248.71	13.585%	$282.4973	$282.50	$282.50	$282.50
7 purchase totals =	$1,098.65		$1,182.5974	$1,182.61	$1,182.65	$1,182.60