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	$54.48	9.432%	$59.6186	$59.62	$59.60	$59.60
Purchase #2	$224.31	11.401%	$249.8836	$249.88	$249.90	$249.90
Purchase #3	$123.85	3.442%	$128.1129	$128.11	$128.10	$128.10
Purchase #4	$194.96	11.726%	$217.821	$217.82	$217.80	$217.80
Purchase #5	$154.47	9.218%	$168.709	$168.71	$168.70	$168.70
Purchase #6	$162.75	7.116%	$174.3313	$174.33	$174.35	$174.30
Purchase #7	$5.37	10.408%	$5.9289	$5.93	$5.95	$5.90
7 purchase totals =	$920.19		$1,004.4053	$1,004.40	$1,004.40	$1,004.30