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	$214.61	10.223%	$236.5496	$236.55	$236.55	$236.50
Purchase #2	$75.79	12.826%	$85.5108	$85.51	$85.50	$85.50
Purchase #3	$48.26	12.232%	$54.1632	$54.16	$54.15	$54.20
Purchase #4	$197.58	12.445%	$222.1688	$222.17	$222.15	$222.20
Purchase #5	$80.50	12.257%	$90.3669	$90.37	$90.35	$90.40
Purchase #6	$21.90	7.128%	$23.461	$23.46	$23.45	$23.50
Purchase #7	$203.40	9.211%	$222.1352	$222.14	$222.15	$222.10
7 purchase totals =	$842.04		$934.3555	$934.36	$934.30	$934.40