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	$64.76	4.584%	$67.7286	$67.73	$67.75	$67.70
Purchase #2	$150.76	9.397%	$164.9269	$164.93	$164.95	$164.90
Purchase #3	$131.73	4.387%	$137.509	$137.51	$137.50	$137.50
Purchase #4	$5.59	12.852%	$6.3084	$6.31	$6.30	$6.30
Purchase #5	$104.94	6.831%	$112.1085	$112.11	$112.10	$112.10
Purchase #6	$188.50	4.550%	$197.0768	$197.08	$197.10	$197.10
Purchase #7	$41.49	3.795%	$43.0645	$43.06	$43.05	$43.10
7 purchase totals =	$687.77		$728.7227	$728.73	$728.75	$728.70