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	$17.87	10.165%	$19.6865	$19.69	$19.70	$19.70
Purchase #2	$47.64	12.516%	$53.6026	$53.60	$53.60	$53.60
Purchase #3	$231.37	10.780%	$256.3117	$256.31	$256.30	$256.30
Purchase #4	$200.43	11.209%	$222.8962	$222.90	$222.90	$222.90
Purchase #5	$80.70	3.581%	$83.5899	$83.59	$83.60	$83.60
Purchase #6	$136.34	4.673%	$142.7112	$142.71	$142.70	$142.70
Purchase #7	$122.83	8.852%	$133.7029	$133.70	$133.70	$133.70
7 purchase totals =	$837.18		$912.5010	$912.50	$912.50	$912.50