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	$143.83	6.756%	$153.5472	$153.55	$153.55	$153.50
Purchase #2	$43.44	5.241%	$45.7167	$45.72	$45.70	$45.70
Purchase #3	$31.76	12.103%	$35.6039	$35.60	$35.60	$35.60
Purchase #4	$212.51	4.702%	$222.5022	$222.50	$222.50	$222.50
Purchase #5	$52.86	6.432%	$56.26	$56.26	$56.25	$56.30
Purchase #6	$136.31	3.441%	$141.0004	$141.00	$141.00	$141.00
Purchase #7	$223.59	12.771%	$252.1447	$252.14	$252.15	$252.10
7 purchase totals =	$844.30		$906.7751	$906.77	$906.75	$906.70