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	$195.77	6.704%	$208.8944	$208.89	$208.90	$208.90
Purchase #2	$168.91	7.402%	$181.4127	$181.41	$181.40	$181.40
Purchase #3	$163.69	10.345%	$180.6237	$180.62	$180.60	$180.60
Purchase #4	$123.77	8.806%	$134.6692	$134.67	$134.65	$134.70
Purchase #5	$101.50	3.403%	$104.954	$104.95	$104.95	$105.00
Purchase #6	$49.72	10.153%	$54.7681	$54.77	$54.75	$54.80
Purchase #7	$100.71	8.814%	$109.5866	$109.59	$109.60	$109.60
7 purchase totals =	$904.07		$974.9087	$974.90	$974.85	$975.00