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	$133.85	6.777%	$142.921	$142.92	$142.90	$142.90
Purchase #2	$174.88	13.509%	$198.5045	$198.50	$198.50	$198.50
Purchase #3	$231.85	9.564%	$254.0241	$254.02	$254.00	$254.00
Purchase #4	$203.46	5.781%	$215.222	$215.22	$215.20	$215.20
Purchase #5	$77.89	10.123%	$85.7748	$85.77	$85.75	$85.80
Purchase #6	$181.86	6.632%	$193.921	$193.92	$193.90	$193.90
Purchase #7	$222.30	11.678%	$248.2602	$248.26	$248.25	$248.30
7 purchase totals =	$1,226.09		$1,338.6276	$1,338.61	$1,338.50	$1,338.60