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	$97.98	4.495%	$102.3842	$102.38	$102.40	$102.40
Purchase #2	$50.32	5.118%	$52.8954	$52.90	$52.90	$52.90
Purchase #3	$107.39	9.181%	$117.2495	$117.25	$117.25	$117.20
Purchase #4	$215.65	12.439%	$242.4747	$242.47	$242.45	$242.50
Purchase #5	$136.61	4.778%	$143.1372	$143.14	$143.15	$143.10
Purchase #6	$242.86	5.351%	$255.8554	$255.86	$255.85	$255.90
Purchase #7	$196.98	8.372%	$213.4712	$213.47	$213.45	$213.50
7 purchase totals =	$1,047.79		$1,127.4676	$1,127.47	$1,127.45	$1,127.50