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	$109.56	12.798%	$123.5815	$123.58	$123.60	$123.60
Purchase #2	$145.94	12.537%	$164.2365	$164.24	$164.25	$164.20
Purchase #3	$148.60	12.411%	$167.0427	$167.04	$167.05	$167.00
Purchase #4	$48.72	5.359%	$51.3309	$51.33	$51.35	$51.30
Purchase #5	$181.43	9.556%	$198.7675	$198.77	$198.75	$198.80
Purchase #6	$156.39	7.558%	$168.21	$168.21	$168.20	$168.20
Purchase #7	$65.77	12.469%	$73.9709	$73.97	$73.95	$74.00
7 purchase totals =	$856.41		$947.1400	$947.14	$947.15	$947.10