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	$40.87	5.673%	$43.1886	$43.19	$43.20	$43.20
Purchase #2	$53.72	11.307%	$59.7941	$59.79	$59.80	$59.80
Purchase #3	$100.94	11.418%	$112.4653	$112.47	$112.45	$112.50
Purchase #4	$232.58	12.694%	$262.1037	$262.10	$262.10	$262.10
Purchase #5	$67.47	6.473%	$71.8373	$71.84	$71.85	$71.80
Purchase #6	$218.50	3.779%	$226.7571	$226.76	$226.75	$226.80
Purchase #7	$238.49	11.264%	$265.3535	$265.35	$265.35	$265.40
7 purchase totals =	$952.57		$1,041.4996	$1,041.50	$1,041.50	$1,041.60