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	$113.87	9.680%	$124.8926	$124.89	$124.90	$124.90
Purchase #2	$64.91	11.774%	$72.5525	$72.55	$72.55	$72.60
Purchase #3	$23.89	4.783%	$25.0327	$25.03	$25.05	$25.00
Purchase #4	$82.91	11.411%	$92.3709	$92.37	$92.35	$92.40
Purchase #5	$10.97	11.166%	$12.1949	$12.19	$12.20	$12.20
Purchase #6	$51.30	5.329%	$54.0338	$54.03	$54.05	$54.00
Purchase #7	$145.62	3.639%	$150.9191	$150.92	$150.90	$150.90
7 purchase totals =	$493.47		$531.9965	$531.98	$532.00	$532.00