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	$205.29	3.170%	$211.7977	$211.80	$211.80	$211.80
Purchase #2	$13.75	13.445%	$15.5987	$15.60	$15.60	$15.60
Purchase #3	$95.39	9.294%	$104.2555	$104.26	$104.25	$104.30
Purchase #4	$161.75	12.731%	$182.3424	$182.34	$182.35	$182.30
Purchase #5	$14.82	10.757%	$16.4142	$16.41	$16.40	$16.40
Purchase #6	$223.38	4.476%	$233.3785	$233.38	$233.40	$233.40
Purchase #7	$73.45	7.421%	$78.9007	$78.90	$78.90	$78.90
7 purchase totals =	$787.83		$842.6877	$842.69	$842.70	$842.70