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	$230.57	4.834%	$241.7158	$241.72	$241.70	$241.70
Purchase #2	$56.40	11.499%	$62.8854	$62.89	$62.90	$62.90
Purchase #3	$159.46	5.709%	$168.5636	$168.56	$168.55	$168.60
Purchase #4	$182.83	9.575%	$200.336	$200.34	$200.35	$200.30
Purchase #5	$69.98	12.555%	$78.766	$78.77	$78.75	$78.80
Purchase #6	$197.29	10.594%	$218.1909	$218.19	$218.20	$218.20
Purchase #7	$214.88	4.662%	$224.8977	$224.90	$224.90	$224.90
7 purchase totals =	$1,111.41		$1,195.3554	$1,195.37	$1,195.35	$1,195.40