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	$167.62	8.109%	$181.2123	$181.21	$181.20	$181.20
Purchase #2	$98.62	4.338%	$102.8981	$102.90	$102.90	$102.90
Purchase #3	$112.53	9.835%	$123.5973	$123.60	$123.60	$123.60
Purchase #4	$113.43	8.718%	$123.3188	$123.32	$123.30	$123.30
Purchase #5	$216.31	5.693%	$228.6245	$228.62	$228.60	$228.60
Purchase #6	$89.99	3.138%	$92.8139	$92.81	$92.80	$92.80
Purchase #7	$151.74	8.235%	$164.2358	$164.24	$164.25	$164.20
7 purchase totals =	$950.24		$1,016.7007	$1,016.70	$1,016.65	$1,016.60