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	$240.88	10.210%	$265.4738	$265.47	$265.45	$265.50
Purchase #2	$15.52	12.732%	$17.496	$17.50	$17.50	$17.50
Purchase #3	$138.58	3.763%	$143.7948	$143.79	$143.80	$143.80
Purchase #4	$89.56	4.401%	$93.5015	$93.50	$93.50	$93.50
Purchase #5	$182.48	6.532%	$194.3996	$194.40	$194.40	$194.40
Purchase #6	$249.52	9.560%	$273.3741	$273.37	$273.35	$273.40
Purchase #7	$150.64	11.483%	$167.938	$167.94	$167.95	$167.90
7 purchase totals =	$1,067.18		$1,155.9778	$1,155.97	$1,155.95	$1,156.00