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	$168.61	10.205%	$185.8167	$185.82	$185.80	$185.80
Purchase #2	$112.82	5.748%	$119.3049	$119.30	$119.30	$119.30
Purchase #3	$149.27	12.758%	$168.3139	$168.31	$168.30	$168.30
Purchase #4	$11.95	5.181%	$12.5691	$12.57	$12.55	$12.60
Purchase #5	$163.39	7.577%	$175.7701	$175.77	$175.75	$175.80
Purchase #6	$210.90	10.542%	$233.1331	$233.13	$233.15	$233.10
Purchase #7	$120.40	11.176%	$133.8559	$133.86	$133.85	$133.90
7 purchase totals =	$937.34		$1,028.7637	$1,028.76	$1,028.70	$1,028.80