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	$107.83	3.639%	$111.7539	$111.75	$111.75	$111.80
Purchase #2	$89.62	10.396%	$98.9369	$98.94	$98.95	$98.90
Purchase #3	$63.67	11.628%	$71.0735	$71.07	$71.05	$71.10
Purchase #4	$20.85	9.181%	$22.7642	$22.76	$22.75	$22.80
Purchase #5	$127.29	3.371%	$131.5809	$131.58	$131.60	$131.60
Purchase #6	$98.42	9.468%	$107.7384	$107.74	$107.75	$107.70
Purchase #7	$102.66	8.759%	$111.652	$111.65	$111.65	$111.70
7 purchase totals =	$610.34		$655.4998	$655.49	$655.50	$655.60