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	$213.87	4.778%	$224.0887	$224.09	$224.10	$224.10
Purchase #2	$246.45	9.698%	$270.3507	$270.35	$270.35	$270.40
Purchase #3	$38.26	13.644%	$43.4802	$43.48	$43.50	$43.50
Purchase #4	$130.90	13.788%	$148.9485	$148.95	$148.95	$148.90
Purchase #5	$150.44	6.728%	$160.5616	$160.56	$160.55	$160.60
Purchase #6	$35.41	10.795%	$39.2325	$39.23	$39.25	$39.20
Purchase #7	$180.41	10.779%	$199.8564	$199.86	$199.85	$199.90
7 purchase totals =	$995.74		$1,086.5186	$1,086.52	$1,086.55	$1,086.60