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	$164.41	9.862%	$180.6241	$180.62	$180.60	$180.60
Purchase #2	$108.53	6.442%	$115.5215	$115.52	$115.50	$115.50
Purchase #3	$131.47	12.526%	$147.9379	$147.94	$147.95	$147.90
Purchase #4	$174.77	13.440%	$198.2591	$198.26	$198.25	$198.30
Purchase #5	$152.79	7.592%	$164.3898	$164.39	$164.40	$164.40
Purchase #6	$222.97	13.550%	$253.1824	$253.18	$253.20	$253.20
Purchase #7	$20.43	5.713%	$21.5972	$21.60	$21.60	$21.60
7 purchase totals =	$975.37		$1,081.5120	$1,081.51	$1,081.50	$1,081.50