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	$227.37	12.641%	$256.1118	$256.11	$256.10	$256.10
Purchase #2	$216.47	8.681%	$235.2618	$235.26	$235.25	$235.30
Purchase #3	$160.88	3.722%	$166.868	$166.87	$166.85	$166.90
Purchase #4	$6.70	9.221%	$7.3178	$7.32	$7.30	$7.30
Purchase #5	$179.60	4.603%	$187.867	$187.87	$187.85	$187.90
Purchase #6	$182.28	7.819%	$196.5325	$196.53	$196.55	$196.50
Purchase #7	$47.41	4.113%	$49.36	$49.36	$49.35	$49.40
7 purchase totals =	$1,020.71		$1,099.3189	$1,099.32	$1,099.25	$1,099.40