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	$162.37	12.426%	$182.5461	$182.55	$182.55	$182.50
Purchase #2	$189.47	5.855%	$200.5635	$200.56	$200.55	$200.60
Purchase #3	$78.56	8.518%	$85.2517	$85.25	$85.25	$85.30
Purchase #4	$76.79	6.150%	$81.5126	$81.51	$81.50	$81.50
Purchase #5	$222.71	8.493%	$241.6248	$241.62	$241.60	$241.60
Purchase #6	$73.93	5.820%	$78.2327	$78.23	$78.25	$78.20
Purchase #7	$54.52	12.806%	$61.5018	$61.50	$61.50	$61.50
7 purchase totals =	$858.35		$931.2332	$931.22	$931.20	$931.20