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	$89.51	10.234%	$98.6705	$98.67	$98.65	$98.70
Purchase #2	$170.99	9.157%	$186.6476	$186.65	$186.65	$186.60
Purchase #3	$238.59	7.634%	$256.804	$256.80	$256.80	$256.80
Purchase #4	$36.34	11.448%	$40.5002	$40.50	$40.50	$40.50
Purchase #5	$240.39	6.334%	$255.6163	$255.62	$255.60	$255.60
Purchase #6	$57.33	5.848%	$60.6827	$60.68	$60.70	$60.70
Purchase #7	$176.81	4.386%	$184.5649	$184.56	$184.55	$184.60
7 purchase totals =	$1,009.96		$1,083.4862	$1,083.48	$1,083.45	$1,083.50