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	$99.38	4.523%	$103.875	$103.88	$103.90	$103.90
Purchase #2	$5.85	3.320%	$6.0442	$6.04	$6.05	$6.00
Purchase #3	$109.85	3.650%	$113.8595	$113.86	$113.85	$113.90
Purchase #4	$176.34	13.470%	$200.093	$200.09	$200.10	$200.10
Purchase #5	$203.82	11.117%	$226.4787	$226.48	$226.50	$226.50
Purchase #6	$217.56	13.870%	$247.7356	$247.74	$247.75	$247.70
Purchase #7	$167.42	4.574%	$175.0778	$175.08	$175.10	$175.10
7 purchase totals =	$980.22		$1,073.1638	$1,073.17	$1,073.25	$1,073.20