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	$210.71	12.732%	$237.5376	$237.54	$237.55	$237.50
Purchase #2	$48.28	10.263%	$53.235	$53.24	$53.25	$53.20
Purchase #3	$43.31	13.685%	$49.237	$49.24	$49.25	$49.20
Purchase #4	$217.27	9.612%	$238.154	$238.15	$238.15	$238.20
Purchase #5	$132.73	5.685%	$140.2757	$140.28	$140.30	$140.30
Purchase #6	$152.67	5.383%	$160.8882	$160.89	$160.90	$160.90
Purchase #7	$177.89	4.187%	$185.3383	$185.34	$185.35	$185.30
7 purchase totals =	$982.86		$1,064.6658	$1,064.68	$1,064.75	$1,064.60