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	$157.98	11.757%	$176.5537	$176.55	$176.55	$176.60
Purchase #2	$160.83	7.605%	$173.0611	$173.06	$173.05	$173.10
Purchase #3	$123.29	6.835%	$131.7169	$131.72	$131.70	$131.70
Purchase #4	$198.45	7.386%	$213.1075	$213.11	$213.10	$213.10
Purchase #5	$211.29	5.847%	$223.6441	$223.64	$223.65	$223.60
Purchase #6	$140.38	8.639%	$152.5074	$152.51	$152.50	$152.50
Purchase #7	$215.33	10.565%	$238.0796	$238.08	$238.10	$238.10
7 purchase totals =	$1,207.55		$1,308.6703	$1,308.67	$1,308.65	$1,308.70