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	$195.45	5.639%	$206.4714	$206.47	$206.45	$206.50
Purchase #2	$52.36	11.737%	$58.5055	$58.51	$58.50	$58.50
Purchase #3	$109.28	4.826%	$114.5539	$114.55	$114.55	$114.60
Purchase #4	$155.40	4.342%	$162.1475	$162.15	$162.15	$162.10
Purchase #5	$168.71	8.106%	$182.3856	$182.39	$182.40	$182.40
Purchase #6	$227.68	13.466%	$258.3394	$258.34	$258.35	$258.30
Purchase #7	$184.36	8.762%	$200.5136	$200.51	$200.50	$200.50
7 purchase totals =	$1,093.24		$1,182.9169	$1,182.92	$1,182.90	$1,182.90