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	$177.27	8.141%	$191.7016	$191.70	$191.70	$191.70
Purchase #2	$60.53	3.618%	$62.72	$62.72	$62.70	$62.70
Purchase #3	$145.61	5.609%	$153.7773	$153.78	$153.80	$153.80
Purchase #4	$172.32	4.523%	$180.114	$180.11	$180.10	$180.10
Purchase #5	$67.50	6.267%	$71.7302	$71.73	$71.75	$71.70
Purchase #6	$230.78	6.810%	$246.4961	$246.50	$246.50	$246.50
Purchase #7	$223.82	3.360%	$231.3404	$231.34	$231.35	$231.30
7 purchase totals =	$1,077.83		$1,137.8796	$1,137.88	$1,137.90	$1,137.80