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	$240.61	10.326%	$265.4554	$265.46	$265.45	$265.50
Purchase #2	$54.83	9.247%	$59.9001	$59.90	$59.90	$59.90
Purchase #3	$187.91	10.401%	$207.4545	$207.45	$207.45	$207.50
Purchase #4	$17.86	8.827%	$19.4365	$19.44	$19.45	$19.40
Purchase #5	$129.69	9.496%	$142.0054	$142.01	$142.00	$142.00
Purchase #6	$193.43	12.718%	$218.0304	$218.03	$218.05	$218.00
Purchase #7	$214.91	8.853%	$233.936	$233.94	$233.95	$233.90
7 purchase totals =	$1,039.24		$1,146.2183	$1,146.23	$1,146.25	$1,146.20