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	$40.30	8.514%	$43.7311	$43.73	$43.75	$43.70
Purchase #2	$154.59	8.630%	$167.9311	$167.93	$167.95	$167.90
Purchase #3	$151.88	10.623%	$168.0142	$168.01	$168.00	$168.00
Purchase #4	$118.86	10.468%	$131.3023	$131.30	$131.30	$131.30
Purchase #5	$165.96	12.374%	$186.4959	$186.50	$186.50	$186.50
Purchase #6	$137.76	4.235%	$143.5941	$143.59	$143.60	$143.60
Purchase #7	$178.31	3.872%	$185.2142	$185.21	$185.20	$185.20
7 purchase totals =	$947.66		$1,026.2829	$1,026.27	$1,026.30	$1,026.20