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	$55.62	6.320%	$59.1352	$59.14	$59.15	$59.10
Purchase #2	$98.72	12.450%	$111.0106	$111.01	$111.00	$111.00
Purchase #3	$216.89	11.164%	$241.1036	$241.10	$241.10	$241.10
Purchase #4	$68.81	3.186%	$71.0023	$71.00	$71.00	$71.00
Purchase #5	$71.89	8.860%	$78.2595	$78.26	$78.25	$78.30
Purchase #6	$161.98	11.827%	$181.1374	$181.14	$181.15	$181.10
Purchase #7	$46.53	4.212%	$48.4898	$48.49	$48.50	$48.50
7 purchase totals =	$720.44		$790.1384	$790.14	$790.15	$790.10