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	$160.88	11.209%	$178.913	$178.91	$178.90	$178.90
Purchase #2	$45.58	7.523%	$49.009	$49.01	$49.00	$49.00
Purchase #3	$41.76	3.694%	$43.3026	$43.30	$43.30	$43.30
Purchase #4	$188.27	4.365%	$196.488	$196.49	$196.50	$196.50
Purchase #5	$71.36	12.819%	$80.5076	$80.51	$80.50	$80.50
Purchase #6	$114.50	7.115%	$122.6467	$122.65	$122.65	$122.60
Purchase #7	$62.61	8.747%	$68.0865	$68.09	$68.10	$68.10
7 purchase totals =	$684.96		$738.9534	$738.96	$738.95	$738.90