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	$188.88	5.284%	$198.8604	$198.86	$198.85	$198.90
Purchase #2	$231.78	13.663%	$263.4481	$263.45	$263.45	$263.40
Purchase #3	$198.41	3.832%	$206.0131	$206.01	$206.00	$206.00
Purchase #4	$54.77	9.356%	$59.8943	$59.89	$59.90	$59.90
Purchase #5	$42.65	4.368%	$44.513	$44.51	$44.50	$44.50
Purchase #6	$95.68	6.487%	$101.8868	$101.89	$101.90	$101.90
Purchase #7	$190.68	9.482%	$208.7603	$208.76	$208.75	$208.80
7 purchase totals =	$1,002.85		$1,083.3760	$1,083.37	$1,083.35	$1,083.40