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	$155.70	11.432%	$173.4996	$173.50	$173.50	$173.50
Purchase #2	$171.77	5.608%	$181.4029	$181.40	$181.40	$181.40
Purchase #3	$101.89	9.774%	$111.8487	$111.85	$111.85	$111.80
Purchase #4	$218.74	7.838%	$235.8848	$235.88	$235.90	$235.90
Purchase #5	$236.27	8.156%	$255.5402	$255.54	$255.55	$255.50
Purchase #6	$217.83	3.492%	$225.4366	$225.44	$225.45	$225.40
Purchase #7	$168.78	8.170%	$182.5693	$182.57	$182.55	$182.60
7 purchase totals =	$1,270.98		$1,366.1821	$1,366.18	$1,366.20	$1,366.10