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	$101.48	10.194%	$111.8249	$111.82	$111.80	$111.80
Purchase #2	$125.31	13.587%	$142.3359	$142.34	$142.35	$142.30
Purchase #3	$100.87	12.317%	$113.2942	$113.29	$113.30	$113.30
Purchase #4	$96.49	9.676%	$105.8264	$105.83	$105.85	$105.80
Purchase #5	$167.44	4.371%	$174.7588	$174.76	$174.75	$174.80
Purchase #6	$46.49	8.287%	$50.3426	$50.34	$50.35	$50.30
Purchase #7	$125.99	8.487%	$136.6828	$136.68	$136.70	$136.70
7 purchase totals =	$764.07		$835.0656	$835.06	$835.10	$835.00