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	$239.45	9.118%	$261.2831	$261.28	$261.30	$261.30
Purchase #2	$86.53	4.688%	$90.5865	$90.59	$90.60	$90.60
Purchase #3	$91.71	12.525%	$103.1967	$103.20	$103.20	$103.20
Purchase #4	$20.63	12.771%	$23.2647	$23.26	$23.25	$23.30
Purchase #5	$164.44	9.247%	$179.6458	$179.65	$179.65	$179.60
Purchase #6	$189.81	5.535%	$200.316	$200.32	$200.30	$200.30
Purchase #7	$191.64	4.679%	$200.6068	$200.61	$200.60	$200.60
7 purchase totals =	$984.21		$1,058.8996	$1,058.91	$1,058.90	$1,058.90