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	$203.42	13.508%	$230.898	$230.90	$230.90	$230.90
Purchase #2	$64.68	12.205%	$72.5742	$72.57	$72.55	$72.60
Purchase #3	$243.66	9.162%	$265.9841	$265.98	$266.00	$266.00
Purchase #4	$81.94	13.385%	$92.9077	$92.91	$92.90	$92.90
Purchase #5	$170.47	11.713%	$190.4372	$190.44	$190.45	$190.40
Purchase #6	$177.79	10.730%	$196.8669	$196.87	$196.85	$196.90
Purchase #7	$138.99	9.518%	$152.2191	$152.22	$152.20	$152.20
7 purchase totals =	$1,080.95		$1,201.8872	$1,201.89	$1,201.85	$1,201.90