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	$212.29	9.259%	$231.9459	$231.95	$231.95	$231.90
Purchase #2	$139.83	3.357%	$144.5241	$144.52	$144.50	$144.50
Purchase #3	$98.99	6.121%	$105.0492	$105.05	$105.05	$105.00
Purchase #4	$207.93	12.270%	$233.443	$233.44	$233.45	$233.40
Purchase #5	$62.41	8.488%	$67.7074	$67.71	$67.70	$67.70
Purchase #6	$36.29	12.837%	$40.9485	$40.95	$40.95	$40.90
Purchase #7	$154.50	11.280%	$171.9276	$171.93	$171.95	$171.90
7 purchase totals =	$912.24		$995.5457	$995.55	$995.55	$995.30