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	$63.73	12.571%	$71.7415	$71.74	$71.75	$71.70
Purchase #2	$86.94	3.622%	$90.089	$90.09	$90.10	$90.10
Purchase #3	$28.50	13.131%	$32.2423	$32.24	$32.25	$32.20
Purchase #4	$78.38	10.866%	$86.8968	$86.90	$86.90	$86.90
Purchase #5	$150.60	5.270%	$158.5366	$158.54	$158.55	$158.50
Purchase #6	$47.86	10.227%	$52.7546	$52.75	$52.75	$52.80
Purchase #7	$243.33	9.562%	$266.5972	$266.60	$266.60	$266.60
7 purchase totals =	$699.34		$758.8580	$758.86	$758.90	$758.80