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	$185.71	3.586%	$192.3696	$192.37	$192.35	$192.40
Purchase #2	$101.28	10.411%	$111.8243	$111.82	$111.80	$111.80
Purchase #3	$232.35	5.291%	$244.6436	$244.64	$244.65	$244.60
Purchase #4	$143.75	6.675%	$153.3453	$153.35	$153.35	$153.30
Purchase #5	$174.80	6.593%	$186.3246	$186.32	$186.30	$186.30
Purchase #6	$162.89	4.138%	$169.6304	$169.63	$169.65	$169.60
Purchase #7	$74.28	10.738%	$82.2562	$82.26	$82.25	$82.30
7 purchase totals =	$1,075.06		$1,140.3940	$1,140.39	$1,140.35	$1,140.30