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	$134.97	13.765%	$153.5486	$153.55	$153.55	$153.50
Purchase #2	$75.33	13.657%	$85.6178	$85.62	$85.60	$85.60
Purchase #3	$174.69	3.193%	$180.2679	$180.27	$180.25	$180.30
Purchase #4	$167.40	11.175%	$186.107	$186.11	$186.10	$186.10
Purchase #5	$76.70	7.477%	$82.4349	$82.43	$82.45	$82.40
Purchase #6	$59.47	8.255%	$64.3792	$64.38	$64.40	$64.40
Purchase #7	$227.83	9.137%	$248.6468	$248.65	$248.65	$248.60
7 purchase totals =	$916.39		$1,001.0022	$1,001.01	$1,001.00	$1,000.90