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	$204.82	11.108%	$227.5714	$227.57	$227.55	$227.60
Purchase #2	$58.38	6.462%	$62.1525	$62.15	$62.15	$62.20
Purchase #3	$136.27	12.595%	$153.4332	$153.43	$153.45	$153.40
Purchase #4	$160.28	6.342%	$170.445	$170.45	$170.45	$170.40
Purchase #5	$42.90	4.485%	$44.8241	$44.82	$44.80	$44.80
Purchase #6	$151.87	8.258%	$164.4114	$164.41	$164.40	$164.40
Purchase #7	$173.48	7.867%	$187.1277	$187.13	$187.15	$187.10
7 purchase totals =	$928.00		$1,009.9653	$1,009.96	$1,009.95	$1,009.90