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	$37.61	10.601%	$41.597	$41.60	$41.60	$41.60
Purchase #2	$23.90	5.754%	$25.2752	$25.28	$25.30	$25.30
Purchase #3	$36.29	6.343%	$38.5919	$38.59	$38.60	$38.60
Purchase #4	$196.25	3.323%	$202.7714	$202.77	$202.75	$202.80
Purchase #5	$128.73	9.217%	$140.595	$140.60	$140.60	$140.60
Purchase #6	$112.47	13.715%	$127.8953	$127.90	$127.90	$127.90
Purchase #7	$247.95	13.158%	$280.5753	$280.58	$280.60	$280.60
7 purchase totals =	$783.20		$857.3011	$857.32	$857.35	$857.40