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	$46.39	3.124%	$47.8392	$47.84	$47.85	$47.80
Purchase #2	$145.62	11.430%	$162.2644	$162.26	$162.25	$162.30
Purchase #3	$217.58	12.544%	$244.8732	$244.87	$244.85	$244.90
Purchase #4	$114.37	11.508%	$127.5317	$127.53	$127.55	$127.50
Purchase #5	$40.92	10.340%	$45.1511	$45.15	$45.15	$45.20
Purchase #6	$210.43	6.671%	$224.4678	$224.47	$224.45	$224.50
Purchase #7	$109.55	10.287%	$120.8194	$120.82	$120.80	$120.80
7 purchase totals =	$884.86		$972.9468	$972.94	$972.90	$973.00