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	$40.78	12.618%	$45.9256	$45.93	$45.95	$45.90
Purchase #2	$48.50	4.493%	$50.6791	$50.68	$50.70	$50.70
Purchase #3	$102.97	11.322%	$114.6283	$114.63	$114.65	$114.60
Purchase #4	$45.67	10.632%	$50.5256	$50.53	$50.55	$50.50
Purchase #5	$171.28	5.729%	$181.0926	$181.09	$181.10	$181.10
Purchase #6	$79.28	3.869%	$82.3473	$82.35	$82.35	$82.30
Purchase #7	$48.90	9.860%	$53.7215	$53.72	$53.70	$53.70
7 purchase totals =	$537.38		$578.9200	$578.93	$579.00	$578.80