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	$82.66	7.279%	$88.6768	$88.68	$88.70	$88.70
Purchase #2	$14.43	9.759%	$15.8382	$15.84	$15.85	$15.80
Purchase #3	$205.89	8.310%	$222.9995	$223.00	$223.00	$223.00
Purchase #4	$85.70	13.558%	$97.3192	$97.32	$97.30	$97.30
Purchase #5	$249.52	9.628%	$273.5438	$273.54	$273.55	$273.50
Purchase #6	$112.78	13.429%	$127.9252	$127.93	$127.95	$127.90
Purchase #7	$182.41	5.745%	$192.8895	$192.89	$192.90	$192.90
7 purchase totals =	$933.39		$1,019.1922	$1,019.20	$1,019.25	$1,019.10