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	$233.39	10.191%	$257.1748	$257.17	$257.15	$257.20
Purchase #2	$145.49	3.220%	$150.1748	$150.17	$150.15	$150.20
Purchase #3	$154.35	3.745%	$160.1304	$160.13	$160.15	$160.10
Purchase #4	$196.32	10.752%	$217.4283	$217.43	$217.45	$217.40
Purchase #5	$86.38	4.468%	$90.2395	$90.24	$90.25	$90.20
Purchase #6	$153.86	11.314%	$171.2677	$171.27	$171.25	$171.30
Purchase #7	$181.84	8.143%	$196.6472	$196.65	$196.65	$196.60
7 purchase totals =	$1,151.63		$1,243.0627	$1,243.06	$1,243.05	$1,243.00