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	$10.69	3.757%	$11.0916	$11.09	$11.10	$11.10
Purchase #2	$38.73	4.147%	$40.3361	$40.34	$40.35	$40.30
Purchase #3	$166.57	11.531%	$185.7772	$185.78	$185.80	$185.80
Purchase #4	$35.62	4.500%	$37.2229	$37.22	$37.20	$37.20
Purchase #5	$86.60	6.676%	$92.3814	$92.38	$92.40	$92.40
Purchase #6	$169.27	9.269%	$184.9596	$184.96	$184.95	$185.00
Purchase #7	$5.64	13.182%	$6.3835	$6.38	$6.40	$6.40
7 purchase totals =	$513.12		$558.1523	$558.15	$558.20	$558.20