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	$82.83	8.454%	$89.8324	$89.83	$89.85	$89.80
Purchase #2	$233.47	7.569%	$251.1413	$251.14	$251.15	$251.10
Purchase #3	$114.78	10.829%	$127.2095	$127.21	$127.20	$127.20
Purchase #4	$164.70	4.401%	$171.9484	$171.95	$171.95	$171.90
Purchase #5	$79.92	8.561%	$86.762	$86.76	$86.75	$86.80
Purchase #6	$34.43	3.607%	$35.6719	$35.67	$35.65	$35.70
Purchase #7	$214.26	4.246%	$223.3575	$223.36	$223.35	$223.40
7 purchase totals =	$924.39		$985.9230	$985.92	$985.90	$985.90