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	$151.47	11.159%	$168.3725	$168.37	$168.35	$168.40
Purchase #2	$122.83	7.367%	$131.8789	$131.88	$131.90	$131.90
Purchase #3	$157.42	11.396%	$175.3596	$175.36	$175.35	$175.40
Purchase #4	$103.73	12.393%	$116.5853	$116.59	$116.60	$116.60
Purchase #5	$218.80	9.714%	$240.0542	$240.05	$240.05	$240.10
Purchase #6	$131.94	6.779%	$140.8842	$140.88	$140.90	$140.90
Purchase #7	$101.74	7.434%	$109.3034	$109.30	$109.30	$109.30
7 purchase totals =	$987.93		$1,082.4381	$1,082.43	$1,082.45	$1,082.60