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	$214.91	7.211%	$230.4072	$230.41	$230.40	$230.40
Purchase #2	$71.46	9.359%	$78.1479	$78.15	$78.15	$78.10
Purchase #3	$119.86	9.461%	$131.2	$131.20	$131.20	$131.20
Purchase #4	$67.88	4.391%	$70.8606	$70.86	$70.85	$70.90
Purchase #5	$39.92	7.392%	$42.8709	$42.87	$42.85	$42.90
Purchase #6	$6.64	9.437%	$7.2666	$7.27	$7.25	$7.30
Purchase #7	$98.91	5.474%	$104.3243	$104.32	$104.30	$104.30
7 purchase totals =	$619.58		$665.0775	$665.08	$665.00	$665.10