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	$95.57	4.850%	$100.2051	$100.21	$100.20	$100.20
Purchase #2	$124.41	13.644%	$141.3845	$141.38	$141.40	$141.40
Purchase #3	$186.56	6.637%	$198.942	$198.94	$198.95	$198.90
Purchase #4	$102.93	6.322%	$109.4372	$109.44	$109.45	$109.40
Purchase #5	$250.40	5.380%	$263.8715	$263.87	$263.85	$263.90
Purchase #6	$21.84	13.473%	$24.7825	$24.78	$24.80	$24.80
Purchase #7	$164.87	11.650%	$184.0774	$184.08	$184.10	$184.10
7 purchase totals =	$946.58		$1,022.7002	$1,022.70	$1,022.75	$1,022.70