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	$141.76	6.446%	$150.8978	$150.90	$150.90	$150.90
Purchase #2	$113.79	9.820%	$124.9642	$124.96	$124.95	$125.00
Purchase #3	$173.67	7.404%	$186.5285	$186.53	$186.55	$186.50
Purchase #4	$242.70	11.286%	$270.0911	$270.09	$270.10	$270.10
Purchase #5	$75.88	9.231%	$82.8845	$82.88	$82.90	$82.90
Purchase #6	$104.44	6.343%	$111.0646	$111.06	$111.05	$111.10
Purchase #7	$112.86	3.492%	$116.8011	$116.80	$116.80	$116.80
7 purchase totals =	$965.10		$1,043.2318	$1,043.22	$1,043.25	$1,043.30