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	$168.90	11.133%	$187.7036	$187.70	$187.70	$187.70
Purchase #2	$49.32	13.505%	$55.9807	$55.98	$56.00	$56.00
Purchase #3	$162.34	12.546%	$182.7072	$182.71	$182.70	$182.70
Purchase #4	$164.36	9.228%	$179.5271	$179.53	$179.55	$179.50
Purchase #5	$62.52	4.493%	$65.329	$65.33	$65.35	$65.30
Purchase #6	$103.89	9.552%	$113.8136	$113.81	$113.80	$113.80
Purchase #7	$122.77	3.759%	$127.3849	$127.38	$127.40	$127.40
7 purchase totals =	$834.10		$912.4461	$912.44	$912.50	$912.40