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	$190.66	11.342%	$212.2847	$212.28	$212.30	$212.30
Purchase #2	$96.58	12.377%	$108.5337	$108.53	$108.55	$108.50
Purchase #3	$175.78	11.647%	$196.2531	$196.25	$196.25	$196.30
Purchase #4	$151.81	6.865%	$162.2318	$162.23	$162.25	$162.20
Purchase #5	$142.46	12.735%	$160.6023	$160.60	$160.60	$160.60
Purchase #6	$17.95	9.141%	$19.5908	$19.59	$19.60	$19.60
Purchase #7	$224.71	9.651%	$246.3968	$246.40	$246.40	$246.40
7 purchase totals =	$999.95		$1,105.8932	$1,105.88	$1,105.95	$1,105.90