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	$24.78	5.386%	$26.1147	$26.11	$26.10	$26.10
Purchase #2	$189.25	3.712%	$196.275	$196.28	$196.30	$196.30
Purchase #3	$12.96	10.828%	$14.3633	$14.36	$14.35	$14.40
Purchase #4	$89.52	12.235%	$100.4728	$100.47	$100.45	$100.50
Purchase #5	$206.62	8.615%	$224.4203	$224.42	$224.40	$224.40
Purchase #6	$119.58	6.405%	$127.2391	$127.24	$127.25	$127.20
Purchase #7	$224.60	3.514%	$232.4924	$232.49	$232.50	$232.50
7 purchase totals =	$867.31		$921.3776	$921.37	$921.35	$921.40