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	$98.95	13.429%	$112.238	$112.24	$112.25	$112.20
Purchase #2	$62.32	12.858%	$70.3331	$70.33	$70.35	$70.30
Purchase #3	$145.50	13.798%	$165.5761	$165.58	$165.60	$165.60
Purchase #4	$152.48	9.508%	$166.9778	$166.98	$167.00	$167.00
Purchase #5	$232.34	10.129%	$255.8737	$255.87	$255.85	$255.90
Purchase #6	$215.28	10.711%	$238.3386	$238.34	$238.35	$238.30
Purchase #7	$119.57	7.350%	$128.3584	$128.36	$128.35	$128.40
7 purchase totals =	$1,026.44		$1,137.6957	$1,137.70	$1,137.75	$1,137.70