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	$85.64	9.334%	$93.6336	$93.63	$93.65	$93.60
Purchase #2	$199.37	12.175%	$223.6433	$223.64	$223.65	$223.60
Purchase #3	$136.82	7.508%	$147.0924	$147.09	$147.10	$147.10
Purchase #4	$241.38	6.678%	$257.4994	$257.50	$257.50	$257.50
Purchase #5	$162.67	6.386%	$173.0581	$173.06	$173.05	$173.10
Purchase #6	$92.84	3.694%	$96.2695	$96.27	$96.25	$96.30
Purchase #7	$85.31	6.387%	$90.7587	$90.76	$90.75	$90.80
7 purchase totals =	$1,004.03		$1,081.9550	$1,081.95	$1,081.95	$1,082.00