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	$117.55	6.287%	$124.9404	$124.94	$124.95	$124.90
Purchase #2	$34.34	3.714%	$35.6154	$35.62	$35.60	$35.60
Purchase #3	$14.85	6.336%	$15.7909	$15.79	$15.80	$15.80
Purchase #4	$178.59	8.304%	$193.4201	$193.42	$193.40	$193.40
Purchase #5	$112.62	13.404%	$127.7156	$127.72	$127.70	$127.70
Purchase #6	$83.35	3.636%	$86.3806	$86.38	$86.40	$86.40
Purchase #7	$125.25	4.804%	$131.267	$131.27	$131.25	$131.30
7 purchase totals =	$666.55		$715.1300	$715.14	$715.10	$715.10